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Respiratory Gas Exchange in the Placenta

Lawrence D. Longo

10.1002/cphy.cp030418

Source: Supplement 13: Handbook of Physiology, The Respiratory System, Gas Exchange

Originally published: 1987

Published online: January 2011

Full Article on Wiley Online Library



Abstract

The sections in this article are:

1 The Placenta
1.1 Placental Exchange and Fetal Oxygenation
1.2 Questions to Consider
2 Maternal Blood O2 Affinity and Capacity
2.1 Hemoglobin
2.2 Blood O2 Affinity and HbO2 Saturation Curve
2.3 Blood O2 Capacity
3 Fetal Blood O2 Affinity and Capacity
3.1 Fetal Hb
3.2 Blood O2 Affinity
3.3 Blood O2 Capacity
4 Interrelations of Maternal and Fetal Blood O2 Affinity and Capacity
4.1 General Considerations
4.2 Species Differences
5 Transplacental Diffusion
5.1 Mean Maternal‐to‐Fetal O2 Tension Differences
5.2 Placental Diffusing Capacity
5.3 Role of Hb Reaction Rates
5.4 Possible Facilitated O2 Transport
5.5 Alterations in Placental Diffusing Capacity
5.6 Placental O2 Consumption
5.7 Summary
6 Variations in Maternal and Fetal O2 Tensions
6.1 Theoretical Considerations
6.2 Experimental Studies
6.3 Clinical Implications
7 Variations in Maternal and Fetal O2 Affinity
7.1 Theoretical Considerations
7.2 Decrease in Fetal Blood O2 Affinity by Intrauterine Transfusion
7.3 Changes in O2 Affinity Due to Hemoglobinopathies
7.4 Maternal Hyperventilation
7.5 Carbon Monoxide Effects
8 Placental CO2 Exchange
8.1 Forms of CO2
8.2 Carbon Dioxide Dissociation Curves
8.3 Transplacental CO2 Exchange
8.4 Haldane and Bohr Effects
8.5 Importance of Various Factors on CO2 Exchange
8.6 Umbilical‐to‐ Uterine Venous CO2 Tension Differences
8.7 Interrelations of Placental CO2 and H2O Exchange
8.8 Conclusions
9 Variations in Rate of Maternal and Fetal Placental HB and O2 Flows
9.1 General Considerations
9.2 Theoretical Considerations
9.3 Experimental Studies
9.4 Clinical Implications of Altered Placental Flows
10 Interrelations of Maternal and Fetal Placental Flows and O2 Exchange
10.1 Distribution of Maternal and Fetal Placental Flows
10.2 “Sluice” or “Waterfall” Flow in Placental Vessels
10.3 Uterine Contractions and O2 Exchange
10.4 Importance of Various Parameters in O2 Transfer
10.5 Summary Equations
10.6 Graphical Analysis of Placental O2 and CO2 Exchange
11 Some Comparisons of Blood Flow and Gas Exchange in the Placenta and Lung
12 Conclusions
Figure 1. Figure 1.

A. Near‐term human placental villus showing well‐differentiated syncytiotrophoblast with its border folded with tufts of microvilli facing maternal intervillous space. Large cytotrophoblast cell is on left and fetal capillary contains several erythrocytes. × 7,350. B. Scanning electron micrograph of 28‐day rhesus monkey villus with fetal capillary containing erythrocytes. × 2,250.

Courtesy of B. F. King
Figure 2. Figure 2.

Schematic illustration of functional anatomy and morphology of placental barrier of several species. Numerical values indicate typical O2 tensions (, Torr) for inflowing and outflowing maternal and fetal blood.
Figure 3. Figure 3.

Cascade of from air to alveolar gas, arterial and uterine venous blood of maternal organism, fetal umbilical venous and arterial blood, and cristae of fetal mitochondria.
Figure 4. Figure 4.

Changes in human maternal (line 2) and fetal (line 1) hemoglobin (Hb) concentrations and fetal mean corpuscular volume (line 3) during course of gestation.
Figure 5. Figure 5.

HbO2 saturation curves for human maternal and near‐term fetal blood. Maternal and fetal Hb‐O2 affinities (P50) are 26.5 and 20 Torr, respectively. A and V, maternal arterial and venous values, respectively, under standard conditions; a and v, umbilical arterial and venous values, respectively; V′, a′, and v′, probable in vivo maternal venous, umbilical arterial, and umbilical venous values, respectively.
Figure 6. Figure 6.

Blood O2 content as function of for maternal ([Hb]m = 12 g · dl−1 and Pm50 = 26.5 Torr) and near‐term fetal ([Hb]f = 16.5 g · dl−1 and Pf50 = 20 Torr) blood. Asterisks, maternal and fetal ; A and V, maternal arterial and venous values; a and v, umbilical arterial and venous values.
Figure 7. Figure 7.

Relation of blood O2 capacity of fetus to that of mother in various species. □, Camel; ☆, cat; , chicken; ▪, cow; ♦, elephant; +, goat; , guinea pig; , hamster; ▴, human; , llama; , pig; ⋄, rabbit; ⊖, rat; Δ and , rhesus monkey; ○, seal; , sheep. Line of identity is shown.
Figure 8. Figure 8.

Relation of blood O2 affinity of fetus to that of mother in various species. Symbols are as in Fig. 7, with the addition of × for baboon and for dog.
Figure 9. Figure 9.

Diagrammatic representation of time course of change in in maternal and fetal blood during single transit in placental exchange vessels. Dashed lines, values assuming that values in uterine and umbilical veins are the same as those of maternal and fetal end capillaries, which is probably incorrect; long arrow, average maternal‐to‐fetal difference of ∼30 Torr calculated on this basis. Solid lines, time courses of changes in values in maternal and fetal placental exchange vessels calculated from measurements of placental CO diffusing capacity; short arrow, probable true maternal‐to‐fetal difference of 5–7 Torr based on calculations of placental diffusing capacity for CO (); under these conditions, values in maternal and fetal blood probably reach near equilibrium in end‐capillary vessels.
Figure 10. Figure 10.

Schematic representation of maternal‐to‐fetal partial pressure differences and resistance to diffusion. Total pressure difference (Pm — Pf) consists of 1) difference between interior of maternal erythrocyte and plasma (Pm ‐ ), 2) difference across membrane between maternal and fetal plasma ( ‐ ), and 3) difference between fetal plasma and interior of fetal erythrocyte (, ‐ Pt). Overall resistance to diffusion (1/DP) is sum of individual resistances: 1) effective resistance of maternal blood to diffusion (1/θmVm), 2) resistance of placental membrane per se (1/DM), and 3) resistance of fetal blood (1/θfVf).
Figure 11. Figure 11.

Calculated changes in transient O2 exchange rate and maternal and fetal placental end‐capillary values (dashed curves) and steady‐state maternal and fetal end‐capillary (solid curves) as functions of Dp. Vertical dashed lines, assumed normal value of Dp. During steady‐state conditions, a normal () may be maintained within limits by decreases of fetal arterial (bottom panel).
Figure 12. Figure 12.

Theoretical effects of maternal exercise on placental O2 transfer. Top, contribution of individual factors to net (). Bottom, net effect of these changes on transient and steady‐statetransfer rates. Tf, fetal temperature; Tm, maternal temperature; Hbm, maternal Hb concentration; , maternal arterial ; pHf, fetal arterial pH; pHm, maternal arterial pH; , uteroplacental blood flow.
Figure 13. Figure 13.

Calculated effects of changes in maternal arterial () on transient maternal and fetal end‐capillary values and O2 exchange rate (dashed curves) and steady‐state end‐capillary values and fetal arterial () (solid curves). Moderate increases in above normal values (95 Torr, vertical dashed lines) increase end‐capillary and transient () only slightly, whereas decreases in produce substantial decreases in () and end‐capillary values. Decreases in alone cannot maintain normal () when is below ∼40 Torr.
Figure 14. Figure 14.

Calculated effects of changes in on end‐capillary and O2 exchange rate. Changes in from normal values (20 Torr, vertical dashed lines) result in increases in either end‐capillary or () but not both and may serve to restore to a normal value.
Figure 15. Figure 15.

Effects of experimentally varying on O2 transfer rate and . Solid lines, theoretical curves.

Adapted from Power and Jenkins 276
Figure 16. Figure 16.

Effects of varying on () and outflowing umbilical . Solid lines, theoretical curves.

Adapted from Power and Jenkins 276
Figure 17. Figure 17.

Relation of to that of mother in chronically catheterized sheep (□) and monkeys (Δ) and acutely anesthetized sheep (○).
Figure 18. Figure 18.

values in uterine arterial (•) and venous (○) blood and in umbilical arterial (Δ) and venous (▴) blood as function of . When Pmvo2 was >200 Torr, uterine venous HbO2 was completely saturated and O2 crossing the placenta was almost entirely from that physically dissolved in maternal plasma. In all cases, was < .
Figure 19. Figure 19.

Cascade of from ambient air to maternal and fetal blood at ∼5,000 m (dotted line) as compared with that at sea level (solid line).
Figure 20. Figure 20.

Calculated maternal and fetal blood O2 contents as function of when relative positions of maternal and fetal HbO2 saturation curves are identical; i.e., both Pm50 and Pf50 are 26.5 Torr. Asterisks, and ; A and V, maternal arterial and venous values; a and v, umbilical arterial and venous values.
Figure 21. Figure 21.

Maternal and fetal blood O2 contents as function of when relative positions of maternal and fetal HbO2 saturation curves are reversed. In this instance, affinity of maternal blood is normal (Pm50 = 26.5 Torr), whereas that of fetus is increased (Pf50 = 35 Torr) due to Hb Kansas replacing Hb A. Symbols are as in Fig. 20.
Figure 22. Figure 22.

Maternal and fetal blood O2 contents as function of when maternal and fetal HbO2 saturation curves are reversed. In this instance, Pm50 = 12 Torr and [Hb]m = 15 g · dl−1, whereas Pf50 = 20 Torr. Symbols are as in Fig. 20.
Figure 23. Figure 23.

Human maternal and fetal HbO2 saturation curves showing CO effects. The HbO2 saturation ([HbO2]) is that percentage of Hb not bound as HbCO.
Figure 24. Figure 24.

Calculated O2 content vs. of human blood with [HbCO]f = 0% and 10% and [HbCO]m = 0% and 9.4%. [Hb]m and [Hb]f are assumed to be 12 and 16.5 g · dl−1, respectively. Normal arteriovenous O2 difference of 5 ml · dl−1 is assumed for both the uterus and its contents and the fetus. Figure depicts mechanism accounting for reduction of umbilical artery and vein O2 tensions and contents resulting from elevated [HbCO].
Figure 25. Figure 25.

Dissociation curves for CO2 in human maternal and fetal blood showing effects of O2 saturation and base deficit, a, Adult deoxygenated blood; b, adult oxygenated blood; c, pregnant women and fetuses; d, fetal blood. Heavy lines, positions expected for maternal and fetal blood based on degree of oxygenation.

Adapted from Eastman et al. 95
Figure 26. Figure 26.

Effect of changes in various factors on transient placental CO2 transfer rate. To facilitate comparison, values are plotted as percent changes from assumed normal values. Slope of each curve at 100% may be used as index of relative sensitivity of CO2 transfer to that factor.

Adapted from Hill et al. 139
Figure 27. Figure 27.

Time course of during single transit through exchange vessels. Solid lines, values within erythrocytes; broken lines, values in plasma. Changes occurring after blood leaves exchange area are plotted on right with scale compressed 40 times.

Adapted from Hill et al. 139
Figure 28. Figure 28.

Calculated effects of changes in maternal placental blood flow, [Hb], Hb flow, and O2 flow on transient maternal and fetal placental end‐capillary values and () (dashed lines) and on steady‐state end‐capillary values and (solid lines).
Figure 29. Figure 29.

Calculated effects of changes in fetal placental blood flow, [Hb], Hb flow, and O2 flow on transient maternal and fetal placental end‐capillary values and () (dashed lines) and on steady‐state end‐capillary values and (solid lines).
Figure 30. Figure 30.

Relations between venous outflow , placental O2 transfer, and fetal cotyledonary flow in perfused isolated sheep and rabbit placentas. Solid lines, predicted relations using mathematical model.

Adapted from Power and Jenkins 276
Figure 31. Figure 31.

Calculated blood O2 content as function of in presence of maternal anemia ([Hb]m = 5.75 g · dl−1) with associated slight increase in O2 affinity (Pm50 = 28 Torr). A and V, maternal arterial and venous values; a and v, umbilical arterial and venous values.
Figure 32. Figure 32.

Calculated blood O2 content as function of in presence of fetal anemia ([Hb]f = 8.25 g · dl−1). Symbols are as in Fig. 31.
Figure 33. Figure 33.

Total uterine vein‐to‐umbilical vein difference at various values of (solid line). Contribution of distribution effect is shown over entire range of values (dashed line) assuming that distribution of maternal to fetal flow () at higher values is similar to that during normal oxygenation. Diffusion effect (shaded area) is shown to be insignificant when exceeds 100 Torr. Dotted line, maternal‐to‐fetal venous difference produced by 15% maternal shunt. Sum of various factors must represent total of this difference.

Adapted from Longo and Power 201
Figure 34. Figure 34.

Volume of maternal () and fetal () placental flows required to exchange 1 ml of O2. As ratio of to increases above 1.0, progressively more is required. This occurs because equilibration occurs at higher and greater saturation of maternal Hb; therefore less O2 is removed from each milliliter of maternal blood. Similarly, fetal blood undergoes greatest changes in [O2] with high ratios; therefore less fetal flow is required. Sum of both curves equals total maternal and fetal flow (dotted line). Optimum ratio for O2 transport in terms of total flow is ∼0.9.

Adapted from Power and Longo 277
Figure 35. Figure 35.

Effects of changes in various factors on transient placental O2 exchange rate. Results are normalized by plotting percent change in () as function of percent change in assumed normal value of given factor. As in Fig. 26, slope of each curve at 100% of normal value indicates relative sensitivity of O2 exchange rate to that factor. () is most sensitive to umbilical arterial , followed closely by total, maternal, and fetal flow rates and O2 affinity of maternal and fetal blood. Curves for maternal and fetal [Hb] are superimposed on and curves. Pm and Pf, maternal and fetal values; Dp, placental diffusing capacity.

Adapted from Longo et al. 200


Figure 1.

A. Near‐term human placental villus showing well‐differentiated syncytiotrophoblast with its border folded with tufts of microvilli facing maternal intervillous space. Large cytotrophoblast cell is on left and fetal capillary contains several erythrocytes. × 7,350. B. Scanning electron micrograph of 28‐day rhesus monkey villus with fetal capillary containing erythrocytes. × 2,250.

Courtesy of B. F. King


Figure 2.

Schematic illustration of functional anatomy and morphology of placental barrier of several species. Numerical values indicate typical O2 tensions (, Torr) for inflowing and outflowing maternal and fetal blood.



Figure 3.

Cascade of from air to alveolar gas, arterial and uterine venous blood of maternal organism, fetal umbilical venous and arterial blood, and cristae of fetal mitochondria.



Figure 4.

Changes in human maternal (line 2) and fetal (line 1) hemoglobin (Hb) concentrations and fetal mean corpuscular volume (line 3) during course of gestation.



Figure 5.

HbO2 saturation curves for human maternal and near‐term fetal blood. Maternal and fetal Hb‐O2 affinities (P50) are 26.5 and 20 Torr, respectively. A and V, maternal arterial and venous values, respectively, under standard conditions; a and v, umbilical arterial and venous values, respectively; V′, a′, and v′, probable in vivo maternal venous, umbilical arterial, and umbilical venous values, respectively.



Figure 6.

Blood O2 content as function of for maternal ([Hb]m = 12 g · dl−1 and Pm50 = 26.5 Torr) and near‐term fetal ([Hb]f = 16.5 g · dl−1 and Pf50 = 20 Torr) blood. Asterisks, maternal and fetal ; A and V, maternal arterial and venous values; a and v, umbilical arterial and venous values.



Figure 7.

Relation of blood O2 capacity of fetus to that of mother in various species. □, Camel; ☆, cat; , chicken; ▪, cow; ♦, elephant; +, goat; , guinea pig; , hamster; ▴, human; , llama; , pig; ⋄, rabbit; ⊖, rat; Δ and , rhesus monkey; ○, seal; , sheep. Line of identity is shown.



Figure 8.

Relation of blood O2 affinity of fetus to that of mother in various species. Symbols are as in Fig. 7, with the addition of × for baboon and for dog.



Figure 9.

Diagrammatic representation of time course of change in in maternal and fetal blood during single transit in placental exchange vessels. Dashed lines, values assuming that values in uterine and umbilical veins are the same as those of maternal and fetal end capillaries, which is probably incorrect; long arrow, average maternal‐to‐fetal difference of ∼30 Torr calculated on this basis. Solid lines, time courses of changes in values in maternal and fetal placental exchange vessels calculated from measurements of placental CO diffusing capacity; short arrow, probable true maternal‐to‐fetal difference of 5–7 Torr based on calculations of placental diffusing capacity for CO (); under these conditions, values in maternal and fetal blood probably reach near equilibrium in end‐capillary vessels.



Figure 10.

Schematic representation of maternal‐to‐fetal partial pressure differences and resistance to diffusion. Total pressure difference (Pm — Pf) consists of 1) difference between interior of maternal erythrocyte and plasma (Pm ‐ ), 2) difference across membrane between maternal and fetal plasma ( ‐ ), and 3) difference between fetal plasma and interior of fetal erythrocyte (, ‐ Pt). Overall resistance to diffusion (1/DP) is sum of individual resistances: 1) effective resistance of maternal blood to diffusion (1/θmVm), 2) resistance of placental membrane per se (1/DM), and 3) resistance of fetal blood (1/θfVf).



Figure 11.

Calculated changes in transient O2 exchange rate and maternal and fetal placental end‐capillary values (dashed curves) and steady‐state maternal and fetal end‐capillary (solid curves) as functions of Dp. Vertical dashed lines, assumed normal value of Dp. During steady‐state conditions, a normal () may be maintained within limits by decreases of fetal arterial (bottom panel).



Figure 12.

Theoretical effects of maternal exercise on placental O2 transfer. Top, contribution of individual factors to net (). Bottom, net effect of these changes on transient and steady‐statetransfer rates. Tf, fetal temperature; Tm, maternal temperature; Hbm, maternal Hb concentration; , maternal arterial ; pHf, fetal arterial pH; pHm, maternal arterial pH; , uteroplacental blood flow.



Figure 13.

Calculated effects of changes in maternal arterial () on transient maternal and fetal end‐capillary values and O2 exchange rate (dashed curves) and steady‐state end‐capillary values and fetal arterial () (solid curves). Moderate increases in above normal values (95 Torr, vertical dashed lines) increase end‐capillary and transient () only slightly, whereas decreases in produce substantial decreases in () and end‐capillary values. Decreases in alone cannot maintain normal () when is below ∼40 Torr.



Figure 14.

Calculated effects of changes in on end‐capillary and O2 exchange rate. Changes in from normal values (20 Torr, vertical dashed lines) result in increases in either end‐capillary or () but not both and may serve to restore to a normal value.



Figure 15.

Effects of experimentally varying on O2 transfer rate and . Solid lines, theoretical curves.

Adapted from Power and Jenkins 276


Figure 16.

Effects of varying on () and outflowing umbilical . Solid lines, theoretical curves.

Adapted from Power and Jenkins 276


Figure 17.

Relation of to that of mother in chronically catheterized sheep (□) and monkeys (Δ) and acutely anesthetized sheep (○).



Figure 18.

values in uterine arterial (•) and venous (○) blood and in umbilical arterial (Δ) and venous (▴) blood as function of . When Pmvo2 was >200 Torr, uterine venous HbO2 was completely saturated and O2 crossing the placenta was almost entirely from that physically dissolved in maternal plasma. In all cases, was < .



Figure 19.

Cascade of from ambient air to maternal and fetal blood at ∼5,000 m (dotted line) as compared with that at sea level (solid line).



Figure 20.

Calculated maternal and fetal blood O2 contents as function of when relative positions of maternal and fetal HbO2 saturation curves are identical; i.e., both Pm50 and Pf50 are 26.5 Torr. Asterisks, and ; A and V, maternal arterial and venous values; a and v, umbilical arterial and venous values.



Figure 21.

Maternal and fetal blood O2 contents as function of when relative positions of maternal and fetal HbO2 saturation curves are reversed. In this instance, affinity of maternal blood is normal (Pm50 = 26.5 Torr), whereas that of fetus is increased (Pf50 = 35 Torr) due to Hb Kansas replacing Hb A. Symbols are as in Fig. 20.



Figure 22.

Maternal and fetal blood O2 contents as function of when maternal and fetal HbO2 saturation curves are reversed. In this instance, Pm50 = 12 Torr and [Hb]m = 15 g · dl−1, whereas Pf50 = 20 Torr. Symbols are as in Fig. 20.



Figure 23.

Human maternal and fetal HbO2 saturation curves showing CO effects. The HbO2 saturation ([HbO2]) is that percentage of Hb not bound as HbCO.



Figure 24.

Calculated O2 content vs. of human blood with [HbCO]f = 0% and 10% and [HbCO]m = 0% and 9.4%. [Hb]m and [Hb]f are assumed to be 12 and 16.5 g · dl−1, respectively. Normal arteriovenous O2 difference of 5 ml · dl−1 is assumed for both the uterus and its contents and the fetus. Figure depicts mechanism accounting for reduction of umbilical artery and vein O2 tensions and contents resulting from elevated [HbCO].



Figure 25.

Dissociation curves for CO2 in human maternal and fetal blood showing effects of O2 saturation and base deficit, a, Adult deoxygenated blood; b, adult oxygenated blood; c, pregnant women and fetuses; d, fetal blood. Heavy lines, positions expected for maternal and fetal blood based on degree of oxygenation.

Adapted from Eastman et al. 95


Figure 26.

Effect of changes in various factors on transient placental CO2 transfer rate. To facilitate comparison, values are plotted as percent changes from assumed normal values. Slope of each curve at 100% may be used as index of relative sensitivity of CO2 transfer to that factor.

Adapted from Hill et al. 139


Figure 27.

Time course of during single transit through exchange vessels. Solid lines, values within erythrocytes; broken lines, values in plasma. Changes occurring after blood leaves exchange area are plotted on right with scale compressed 40 times.

Adapted from Hill et al. 139


Figure 28.

Calculated effects of changes in maternal placental blood flow, [Hb], Hb flow, and O2 flow on transient maternal and fetal placental end‐capillary values and () (dashed lines) and on steady‐state end‐capillary values and (solid lines).



Figure 29.

Calculated effects of changes in fetal placental blood flow, [Hb], Hb flow, and O2 flow on transient maternal and fetal placental end‐capillary values and () (dashed lines) and on steady‐state end‐capillary values and (solid lines).



Figure 30.

Relations between venous outflow , placental O2 transfer, and fetal cotyledonary flow in perfused isolated sheep and rabbit placentas. Solid lines, predicted relations using mathematical model.

Adapted from Power and Jenkins 276


Figure 31.

Calculated blood O2 content as function of in presence of maternal anemia ([Hb]m = 5.75 g · dl−1) with associated slight increase in O2 affinity (Pm50 = 28 Torr). A and V, maternal arterial and venous values; a and v, umbilical arterial and venous values.



Figure 32.

Calculated blood O2 content as function of in presence of fetal anemia ([Hb]f = 8.25 g · dl−1). Symbols are as in Fig. 31.



Figure 33.

Total uterine vein‐to‐umbilical vein difference at various values of (solid line). Contribution of distribution effect is shown over entire range of values (dashed line) assuming that distribution of maternal to fetal flow () at higher values is similar to that during normal oxygenation. Diffusion effect (shaded area) is shown to be insignificant when exceeds 100 Torr. Dotted line, maternal‐to‐fetal venous difference produced by 15% maternal shunt. Sum of various factors must represent total of this difference.

Adapted from Longo and Power 201


Figure 34.

Volume of maternal () and fetal () placental flows required to exchange 1 ml of O2. As ratio of to increases above 1.0, progressively more is required. This occurs because equilibration occurs at higher and greater saturation of maternal Hb; therefore less O2 is removed from each milliliter of maternal blood. Similarly, fetal blood undergoes greatest changes in [O2] with high ratios; therefore less fetal flow is required. Sum of both curves equals total maternal and fetal flow (dotted line). Optimum ratio for O2 transport in terms of total flow is ∼0.9.

Adapted from Power and Longo 277


Figure 35.

Effects of changes in various factors on transient placental O2 exchange rate. Results are normalized by plotting percent change in () as function of percent change in assumed normal value of given factor. As in Fig. 26, slope of each curve at 100% of normal value indicates relative sensitivity of O2 exchange rate to that factor. () is most sensitive to umbilical arterial , followed closely by total, maternal, and fetal flow rates and O2 affinity of maternal and fetal blood. Curves for maternal and fetal [Hb] are superimposed on and curves. Pm and Pf, maternal and fetal values; Dp, placental diffusing capacity.

Adapted from Longo et al. 200
References
 1. Abrahamov, A., and C. A. Smith. Oxygen capacity and affinity of blood from erythroblastotic newborns. I. Effects of plasma environment on erythrocytes containing fetal or adult hemoglobin. Am. J. Dis. Child. 97: 375–379, 1959.
 2. Adamson, J. W., J. T. Parer, and G. Stamatoyannopoulos. Erythrocytosis associated with hemoglobin Ranier: oxygen equilibria and marrow regulation. J. Clin. Invest. 48: 1376–1386, 1969.
 3. Adamsons, K., R. W. Beard, and R. E. Myers. Comparison of the composition of arterial, venous, and capillary blood of the fetal monkey during labor. Am. J. Obstet. Gynecol. 107: 435–440, 1970.
 4. Aherne, W., and M. S. Dunnill. Quantitative aspects of placental structure. J. Pathol. Bacteriol. 91: 123–139, 1966.
 5. Allen, D. W., J. Wyman, Jr., and C. H. Smith. The oxygen equilibrium of fetal and adult human hemoglobin. J. Biol. Chem. 203: 81–87, 1953.
 6. Allen, W. W., G. G. Power, and L. D. Longo. Fetal O2 changes in response to hypoxic stress: a mathematical model. J. Appl. Physiol. 42: 179–190, 1977.
 7. Anselmino, K. J., and F. Hoffmann. Die Ursachen des Icterus neonatorum. Arch. Gynaekol. 143: 447–499, 1930.
 8. Anselmino, K. J., and F. Hoffmann. Die Ursachen des Icterus neonatorum. Bemerkungen zu der vorstehenden Arbeit von Haselhorst und Stromberger, zugleich eine Erweiterung unserer Theorie. Arch. Gynaekol. 147: 69–71, 1931.
 9. Bacon, B. J., R. D. Gilbert, P. Kaufmann, A. D. Smith, T. Trevino, and L. D. Longo. Placental anatomy and diffusing capacity in guinea pigs following long‐term maternal hypoxia. Placenta 5: 475–488, 1984.
 10. Baillie, P., G. S. Dawes, C. L. Merlet, and R. Richards. Maternal hyperventilation and foetal hypocapnia in sheep. J. Physiol. Lond. 218: 635–650, 1971.
 11. Barcroft, J. The Respiratory Function of the Blood. Haemoglobin. Cambridge, UK: Cambridge Univ. Press, 1928, pt. 2, p. 52.
 12. Barcroft, J. The conditions of foetal respiration. Lancet 225: 1021–1024, 1933.
 13. Barcroft, J. Researches on Prenatal Life. Oxford, UK: Black‐well, 1946, vol. 1.
 14. Barcroft, J., and D. H. Barron. Observations upon the form and relations of the maternal and fetal vessels in the placenta of the sheep. Anat. Rec. 94: 569–595, 1946.
 15. Barnes, A. C. Discussion. Congenital heart disease in pregnancy, by D. E. Cannell and C. P. Vernon. Am. J. Obstet. Gynecol. 85: 749–750, 1963.
 16. Barron, D. H. The oxygen pressure gradient between the maternal and fetal blood in pregnant sheep. Yale J. Biol. Med. 19: 23–27, 1946.
 17. Barron, D. H., and G. Alexander. Supplementary observations on the oxygen pressure gradient between the maternal and fetal bloods of sheep. Yale J. Biol. Med. 25: 61–66, 1952.
 18. Barron, D. H., and F. C. Battaglia. The oxygen concentration gradient between the plasmas in the maternal and fetal capillaries of the placenta of the rabbit. Yale J. Biol. Med. 28: 197–207, 1955–56.
 19. Barron, D. H., and G. Meschia. A comparative study of the exchange of the respiratory gases across the placenta. Cold Spring Harbor Symp Quant. Biol. 39: 93–103, 1954.
 20. Bartels, H. Carriage of oxygen in the blood of the foetus. In: Development of the Lung, edited by A. V. S. de Reuck and R. Porter. Boston, MA: Little, Brown, 1967, p. 276–296. (Ciba Found. Symp.)
 21. Bartels, H. Prenatal Respiration. Amsterdam: North‐Holland, 1970.
 22. Bartels, H., D. el Yassin, and W. Reinhardt. Comparative studies of placental gas exchange in guinea pigs, rabbits, and goats. Respir. Physiol. 2: 149–162, 1967.
 23. Bartels, H., H. Harms, V. Probst, K. Riegel, and J. Schneider. Sauerstoffbindungskurve, fetales Hamoglobin und Erythrocytenmorphologie bei Frühgeborenen und Säuglingen. Klin. Wochenschr. 37: 664–665, 1959.
 24. Bartels, H., G. Hiller, and W. Reinhardt. Oxygen affinity of chicken blood before and after hatching. Respir. Physiol. 1: 345–356, 1966.
 25. Bartels, H., and W. Moll. Passage of inert substances and oxygen in the human placenta. Pfluegers Arch. 280: 165–177, 1964.
 26. Bartels, H., W. Moll, and J. Metcalfe. Physiology of gas exchange in the human placenta. Am. J. Obstet. Gynecol. 84: 1714–1730, 1962.
 27. Battaglia, F. C. Intrauterine growth retardation. Am. J. Obstet. Gynecol. 106: 1103–1114, 1970.
 28. Battaglia, F. C., W. Bowes, H. R. McGaughey, E. L. Makowski, and G. Meschia. The effect of fetal exchange transfusions with adult blood upon fetal oxygenation. Pediatr. Res. 3: 60–65, 1969.
 29. Bauer, C., W. Jelkmann, and W. Moll. High oxygen affinity of maternal blood reduces fetal weight in rats. Respir. Physiol. 43: 169–178, 1981.
 30. Bauer, C., I. Ludwig, and M. Ludwig. Different effects of 2,3‐diphosphoglycerate and adenosine triphosphate on the oxygen affinity of adult and foetal human haemoglobin. Life Sci. 7: 1339–1343, 1968.
 31. Bauer, C., M. Ludwig, I. Ludwig, and H. Bartels. Factors governing the oxygen affinity of human adult and foetal blood. Respir. Physiol. 7: 271–277, 1969.
 32. Baumann, R., F. Teischel, R. Zoch, and H. Bartels. Changes in red cell 2,3‐diphosphoglycerate concentration as cause of the postnatal decrease of pig blood oxygen affinity. Respir. Physiol. 19: 153–161, 1973.
 33. Beer, R., H. Bartels, and H. A. Raczkowski. Die Saüerstoffdissoziationskurve des fetalen Blutes und der Gasaustausch in der menschlichen Placenta. Pfluegers Arch. 260: 306–319, 1955.
 34. Beer, R., E. Doll, and J. Wenner. Die Verschiebung der Säuerstoffdissoziationskurve des Blutes von Säuglingen während der ersten Lebensmonate. Pfluegers Arch. 265: 526–540, 1958.
 35. Behrman, R. E., J. T. Parer, and M. J. Novy. Acute maternal respiratory alkalosis (hyperventilation) in the pregnant rhesus monkey. Pediatr. Res. 1: 354–363, 1967.
 36. Berfenstam, R. Studies in carbonic anhydrase activity in children. I. Enzyme activity in the blood of infants and children of different ages, particularly in premature infants. Acta Paediatr. Scand. 41: 32–52, 1952.
 37. Berman, W., Jr., R. C. Goodlin, M. A. Heymann, and A. M. Rudolph. Relationships between pressure and flow in the umbilical and uterine circulations of the sheep. Circ. Res. 38: 262–266, 1976.
 38. Betke, K., and E. Kleihauer. Fetaler und bleibender Blutfarbstoff in Erythrozyten und Erythroblasten von menschlichen Feten und Neugeborenen. Blut 4: 241–249, 1958.
 39. Bissonnette, J. M. Control of vascular volume in sheep umbilical circulation. J. Appl. Physiol. 38: 1057–1061, 1975.
 40. Bissonnette, J. M. Regulation of capillary volume in the fetal placental circulation. In: Fetal and Newborn Cardiovascular Physiology. Fetal and Newborn Circulation, edited by L. D. Longo and D. D. Reneau. New York: Garland, 1978, vol. 2, p. 69–80.
 41. Bissonnette, J. M., and R. C. Farrell. Pressure‐flow and pressure‐volume relationships in the fetal placental circulation. J. Appl. Physiol. 35: 355–360, 1973.
 42. Bissonnette, J. M., L. D. Longo, M. J. Novy, Y. Murata, and C. B. Martin, Jr. Placental diffusing capacity and its relation to fetal growth. J. Dev. Physiol. Oxf. 1: 351–359, 1979.
 43. Bissonnette, J. M., and W. K. Wickham. Placental diffusing capacity for carbon monoxide in unanesthetized guinea pigs. Respir. Physiol. 31: 161–168, 1977.
 44. Bissonnette, J. M., W. K. Wickham, and W. H. Drummond. Placental diffusing capacities at varied carbon monoxide tensions. J. Clin. Invest. 59: 1038–1044, 1977.
 45. Blechner, J. N., J. R. Cotter, C. M. Hinkley, and H. Prystowsky. Observations on pregnancy at altitude. II. Transplacental pressure differences of oxygen and carbon dioxide. Am. J. Obstet. Gynecol. 102: 794–805, 1968.
 46. Blechner, J. N., C. Meschia, and D. H. Barron. A study of the acid‐base balance of foetal sheep and goats. Q. J. Exp. Physiol. 45: 60–71, 1960.
 47. Bøe, F. Vascular morphology of the human placenta. Cold Spring Harbor Symp. Quant. Biol. 19: 29–35, 1954.
 48. Borell, U., I. Fernström, and A. Westman. Eine arteriographische Studie des Plazentarkreislaufs. Geburtsh. Frauenheilkd. 18: 1–9, 1958.
 49. Born, G. V. R., G. S. Dawes, and J. C. Mott. Oxygen lack and autonomic nervous control of the foetal circulation in the lamb. J. Physiol. Lond. 134: 149–166, 1956.
 50. Bos, S. E. De mechanische fragiliteit van erythrocyten. Maandschr. Kindergeneeskd. 23: 335–348, 1955.
 51. Boyle, J. W., F. K. Lotgering, and L. D. Longo. Acute embolization of the uteroplacental circulation: uterine blood flow and placental CO diffusing capacity. J. Dev. Physiol. Oxf. 6: 377–386, 1984.
 52. Boyle, R. New pneumatical experiments about respiration. Philos. Trans. R. Soc. Lond. 5: 2011–2031, 1670.
 53. Brinkman, R., and J. H. P. Jonxis. The occurrence of several kinds of haemoglobin in human blood. J. Physiol. Lond. 85: 117–127, 1935.
 54. Brinkman, R., A. Wildschut, and A. Wittermans. On the occurrence of two kinds of haemoglobin in normal human blood. J. Physiol. Lond. 80: 377–387, 1934.
 55. Brosens, I., and H. G. Dixon. The anatomy of the maternal side of the placenta. J. Obstet. Gynaecol. Br. Commonw. 73: 357–363, 1966.
 56. Bruns, P. D., W. A. Bowes, Jr., V. E. Drose, and F. C. Battaglia. Effect of respiratory acidosis on the rabbit fetus in utero. Am. J. Obstet. Gynecol. 87: 1074–1080, 1963.
 57. Bruns, P. D., W. E. Cooper, and V. E. Drose. Maternalfetal oxygen and acid‐base studies and their relationships to hyaline membrane disease in the newborn infant. Am. J. Obstet. Gynecol. 82: 1079–1088, 1962.
 58. Bunn, H. F., B. G. Forget, and H. M. Ranney. Hemoglobinopathies. Major Probl. Intern. Med. 12: 1–291, 1977.
 59. Bunn, H. F., K. H. Gabbay, and P. M. Gallop. The glycosylation of hemoglobin: relevance to diabetes mellitus. Science Wash. DC 200: 21–27, 1978.
 60. Bunn, H. F., D. N. Haney, S. Kamin, K. H. Gabbay, and P. M. Gallop. The biosynthesis of human hemoglobin A1c. Slow glycosylation of hemoglobin in vivo. J. Clin. Invest. 57: 1652–1659, 1976.
 61. Bursaux, E., C. Poyart, P. Guesnon, and B. Teisseire. Comparative effects of CO2 on the affinity for O2 of fetal and adult erythrocytes. Pfluegers Arch. 378: 197–203, 1979.
 62. Butler, L. A., L. D. Longo, and G. G. Power. Placental blood flows and oxygen transfer during uterine contractions: a mathematical model. J. Theor. Biol. 61: 81–95, 1976.
 63. Butler, L. A., L. D. Longo, and G. G. Power. A model of placental parameters during labor contractions. In: Fetal and Newborn Cardiovascular Physiology. Developmental Aspects, edited by L. D. Longo and D. D. Reneau. New York: Garland, 1978, vol. 1, p. 561–578.
 64. Campbell, A. G. M., G. S. Dawes, A. P. Fishman, A. I. Hyman, and G. B. James. The oxygen consumption of the placenta and the foetal membranes in the sheep. J. Physiol. Lond. 182: 439–464, 1966.
 65. Charache, S., and E. A. Murphy. Is placental oxygen transport normal in carriers of high affinity hemoglobins? Colloq. INSERM 70: 285–294, 1977.
 66. Clapp, J. F., III. The relationship between blood flow and oxygen uptake in the uterine and umbilical circulations. Am. J. Obstet. Gynecol. 132: 410–413, 1978.
 67. Clapp, J. F., III, R. M. Abrams, D. Caton, J. R. Cotter, G. B. James, and D. H. Barron. Umbilical blood flow in late gestation: a comparison of simultaneous measurements with two different techniques. Am. J. Obstet. Gynecol. 119: 919–923, 1974.
 68. Coleman, A. J. Absence of harmful effect of maternal hypocapnea in babies delivered at caesarean section. Lancet 1: 813–814, 1967.
 69. Comline, R. S., and I. A. Silver. Factors responsible for the stimulation of the adrenal medulla during asphyxia in the fetal lamb. J. Physiol. Lond. 178: 211–238, 1965.
 70. Comline, R. S., and M. Silver. Daily changes in foetal and maternal blood of conscious pregnant ewes, with catheters in umbilical and uterine vessels. J. Physiol. Lond. 209: 567–586, 1970.
 71. Comline, R. S., and M. Silver. Po2, Pco2 and pH levels in the umbilical and uterine blood of the mare and ewe. J. Physiol. Lond. 209: 587–608, 1970.
 72. Comline, R. S., and M. Silver. A comparative study of blood gas tensions, oxygen affinity and red cell 2,3‐DPG concentrations in foetal and maternal blood in the mare, cow and sow. J. Physiol. Lond. 242: 805–826, 1974.
 73. Cottle, M. K. W., G. R. van Petten, and P. van Muyden. Depression of uterine blood flow in response to cord compression in sheep. Can. J. Physiol. Pharmacol. 60: 825–829, 1982.
 74. Crawford, J. S. Anaesthesia for caesarean section: a proposal for evaluation, with analysis of a method. Br. J. Anaesth. 34: 179–194, 1962.
 75. Creasy, R. K., C. T. Barrett, M. Deswiet, K. V. Kahanpaa, and A. M. Rudolph. Experimental intrauterine growth retardation in the sheep. Am. J. Obstet. Gynecol. 112: 566–573, 1972.
 76. Crenshaw, C., W. E. Huckabee, L. B. Curet, L. Mann, and D. H. Barron. A method for the estimation of the umbilical blood flow in unstressed sheep and goats with some results of its application. Q. J. Exp. Physiol. 53: 65–75, 1968.
 77. Danesino, V. Dispositivi di blocco ed anastomosi arterovenose nei vasi fetali della placenta umana. Arch. Ostet. Ginecol. 55: 251–272, 1959.
 78. Darling, R. C., C. A. Smith, E. Asmussen, and F. M. Cohen. Some properties of human fetal and maternal blood. J. Clin. Invest. 20: 739–747, 1941.
 79. Dawes, G. S. Foetal and Neonatal Physiology. Chicago, IL: Year Book, 1968.
 80. Dawes, G. S., H. N. Jacobson, J. C. Mott, and H. J. Shelley. Some observations on foetal and newborn rhesus monkeys. J. Physiol. Lond. 152: 271–298, 1960.
 81. Dawes, G. S., and J. C. Mott. Changes in O2 distribution and consumption in foetal lambs with variations in umbilical blood flow. J. Physiol. Lond. 170: 524–540, 1964.
 82. Delivoria‐Papadopoulos, M., R. F. Coburn, and R. E. Forster II. The placental diffusing capacity of carbon monoxide in pregnant women at term. In: Respiratory Gas Exchange and Blood Flow in the Placenta, edited by L. D. Longo and H. Bartels. Bethesda, MD: Natl. Inst. Health, 1972, p. 259–265. (No. NIH 73–361.)
 83. De Verdier, C.‐H., and Garby, L. Low binding of 2,3‐diphosphoglycerate to haemoglobin F: a contribution to the knowledge of the binding site and an explanation for the high oxygen affinity of fetal blood. Scand. J. Clin. Lab. Invest. 23: 149–151, 1969.
 84. Dhindsa, D. S., C. J. Sedgwick, and J. Metcalfe. Comparative studies of the respiratory functions of mammalian blood. VIII. Asian elephant (Elephas maximus) and African elephant (Loxodonta africana). Respir. Physiol. 14: 332–342, 1972.
 85. Dijkhuizen, P., A. Buursma, T. M. E. Fongers, A. M. Gerding, B. Oeseburg, and W. G. Zijlstra. The oxygen binding capacity of human haemoglobin. Hüfner's factor redetermined. Pfluegers Arch. 36: 223–231, 1977.
 86. Dill, D. B., A. Graybiel, A. Hurtado, and A. Taquini. Der Gasaustausch in den Lungen im Alter. Z. Alternsforsch 2: 20–33, 1940.
 87. Ditzel, J. Changes in red cell oxygen release capacity in diabetes mellitus. Federation Proc. 38: 2484–2488, 1979.
 88. Ditzel, J., and E. Standl. The problem of tissue oxygenation in diabetes mellitus. I. Its relation to the early functional changes in the microcirculation of diabetic subjects. Acta Med. Scand. Suppl. 578: 49–58, 1975.
 89. Dodds, G. S. The area of the chorionic villi in the full term placenta. Anat. Rec. 24: 287–294, 1922/1923.
 90. Douglas, C. G., J. S. Haldane, and J. B. S. Haldane. The laws of combination of haemoglobin with carbon monoxide and oxygen. J. Physiol. Lond. 44: 275–304, 1912.
 91. Drescher, H., and W. Künzer. Der Blutfarbstoff des menschlichen Feten. Klin. Wochenschr. 32: 92, 1954.
 92. Duncan, S. L. B., and B. V. Lewis. Maternal placental and myometrial blood flow in the pregnant rabbit. J. Physiol. Lond. 202: 471–481, 1969.
 93. Eastman, N. J. Fetal blood studies. V. The role of anesthesia in the production of asphyxia neonatorum. Am. J. Obstet. Gynecol. 31: 563–572, 1936.
 94. Eastman, N. J. Discussion. Oxygen utilization by the human fetus in utero, by S. L. Romney, D. E. Reid, J. Metcalfe, and C. S. Burwell. Am. J. Obstet. Gynecol. 70: 791–799, 1955.
 95. Eastman, N. J., E. M. K. Geilling, and A. M. de Lawdner. Foetal blood studies. IV. The oxygen and carbon‐dioxide dissociation curves of fetal blood. Bull. Johns Hopkins Hosp. 53: 246–254, 1933.
 96. Elliott, R. H., F. G. Hall, and A. St. G. Huggett. The blood volume and oxygen capacity of the foetal blood in the goat. J. Physiol. Lond. 82: 160–171, 1934.
 97. Elsner, R., D. D. Hammond, and H. R. Parker. Circulatory responses to asphyxia in pregnant and fetal animals: a comparative study of Weddell seals and sheep. Yale J. Biol. Med. 42: 202–217, 1969–70.
 98. Faber, J. J. Application of the theory of heat exchangers to the transfer of inert materials in placentas. Circ. Res. 24: 221–234, 1969.
 99. Faber, J. J. Steady‐state methods for the study of placental exchange. Federation Proc. 36: 2640–2646, 1977.
 100. Faber, J. J., C. F. Gault, T. J. Green, and K. L. Thorn‐burg. Fetal blood volume and fetal placental blood flow in lambs. Proc. Soc. Exp. Biol. Med. 142: 340–344, 1973.
 101. Faber, J. J., and F. M. Hart. The rabbit placenta as an organ of diffusional exchange. Comparison with other species by dimensional analysis. Circ. Res. 19: 816–833, 1966.
 102. Faber, J. J., and F. M. Hart. Transfer of charged and uncharged molecules in the placenta of the rabbit. Am. J. Physiol. 213: 890–894, 1967.
 103. Fisher, A., and C. Prys‐Roberts. Maternal pulmonary gas exchange: a study during normal labour and extradural blockade. Anaesthesia 23: 350–356, 1968.
 104. Forster, R. E., II. Some principles governing maternal‐foetal transfer in the placenta. In: Foetal and Neonatal Physiology, edited by K. S. Comline, K. W. Cross, G. S. Dawes, and P. W. Nathanielsz. London: Cambridge Univ. Press, 1973, p. 223–237. (Proc. Sir Joseph Barcroft Centenary Symp., Cambridge, July, 1972.)
 105. Forster, R. E., II, and E. D. Crandall. Time course of exchanges between red cells and extracellular fluid during CO2 uptake. J. Appl. Physiol. 38: 710–718, 1975.
 106. Fracastoro, G. De sympathia et antipathia rerum liber unus. De contagione et contagiosis morbis et curatione. Venice: Iuntae, 1546.
 107. Fuchs, F., T. Spackman, and N. S. Assali. Complexity and nonhomogeneity of the intervillous space. Am. J. Obstet. Gynecol. 86: 226–233, 1963.
 108. Fujikura, T. Retrolental fibroplasia and prematurity in newborn rabbits induced by maternal hyperoxia. Am. J. Obstet. Gynecol. 90: 854–858, 1964.
 109. Fuller, E. O., P. M. Galletti, D. O. Nutter, and R. W. Millard. Hemodynamics of the perfused pregnant sheep uterus. Sci. Abstr. Soc. Gynecol. Invest., 1979, p. 24.
 110. Fuller, E. O., J. W. Manning, D. O. Nutter, and P. M. Gall*etti. A perfused uterine preparation for the study of uterine and fetal physiology. In: Fetal and Newborn Cardiovascular Physiology. Fetal and Newborn Circulation, edited by L. D. Longo and D. D. Reneau. New York: Garland, 1978, vol. 2, p. 421–435.
 111. Gahlenbeck, H., H. Frerking, A. M. Rathschlag‐Schaffner, and H. Bartels. Oxygen and carbon dioxide exchange across the cow placenta during the second part of pregnancy. Respir. Physiol. 4: 119–131, 1968.
 112. Gale, R. E., J. B. Clegg, and E. R. Huehns. Human embryonic haemoglobins Gower 1 and Gower 2. Nature Lond. 280: 162–164, 1979.
 113. Garby, L., S. Sjölin, and J. C. Vuille. Studies on erythro‐kinetics in infancy. V. Estimations of the life span of red cells in the newborn. Acta Paediatr. 53: 165–171, 1964.
 114. Gilbert, R. D., L. A. Cummings, M. R. Juchau, and L. D. Longo. Placental diffusing capacity and fetal development in exercising or hypoxic guinea pigs. J. Appl. Physiol. 46: 828–834, 1979.
 115. Gilman, J. G. Rat embryonic and foetal erythrocytes. High 2,3‐bisphosphoglycerate and ATP and low oxygen affinity in vitro for nucleated embryonic cells. Biochem. J. 192: 355–359, 1980.
 116. Gratzer, W. B., and A. C. Allison. Multiple haemoglobins. Biol. Rev. Lond. 35: 459–506, 1960.
 117. Greiss, F. C., Jr. Effect of labor on uterine blood flow. Observations on gravid ewes. Am. J. Obstet. Gynecol. 93: 917–923, 1965.
 118. Greiss, F. C., Jr., and S. G. Anderson. Uterine blood flow during labor. Clin. Obstet. Gynecol. 11: 96–109, 1968.
 119. Gruenwald, P. Chronic fetal distress and placental insufficiency. Biol. Neonat. 5: 215–265, 1963.
 120. Guilbeau, E. J., D. D. Reneau; and M. H. Knisely. A distributed parameter mathematical analysis of oxygen exchange from maternal to fetal blood in the human placenta. In: Blood Oxygenation, edited by D. Hershey. New York: Plenum, 1970, p. 218–221. (Proc. Int. Symp. on Blood Oxygenation, Univ. of Cincinnati, December, 1969.)
 121. Guilbeau, E. J., D. D. Reneau, and M. H. Knisely. The effects of placental oxygen consumption and the contractions of labor on fetal oxygen supply. A steady and unsteady state mathematical simulation. In: Respiratory Gas Exchange and Blood Flow in the Placenta, edited by L. D. Longo and H. Bartels. Bethesda, MD: Natl. Inst. Health, 1972, p. 297–344. (No. NIH 73–361.)
 122. Gurtner, G. H. Evidence for facilitated transport of oxygen and carbon monoxide. In: Pulmonary Gas Exchange. Organism and Environment, edited by J. B. West. New York: Academic, 1980, vol. 2, p. 205–239.
 123. Gurtner, G. H., and B. Burns. Physiological evidence consistent with the presence of a specific O2 carrier in the placenta. J. Appl. Physiol. 39: 728–734, 1975.
 124. Gurtner, G. H., and B. Burns. Possible facilitated transport of oxygen across the placenta. Nature Lond. 240: 473–475, 1972.
 125. Halbrecht, I., and C. Klibanski. Identification of a new normal embryonic haemoglobin. Nature Lond. 178: 794–795, 1956.
 126. Halbrecht, I., C. Klibanski, and F. BarIlan. Co‐existence of the embryonic (third normal) haemoglobin fraction with erythroblastosis in the blood of two full‐term newborn babies with multiple malformations. Nature Lond. 183: 327–328, 1959.
 127. Halbrecht, I., C. Klibanski, H. Brzoza, and M. Lahav. Further studies on the various hemoglobins and the serum protein fractions in early embryonic life. Am. J. Clin. Pathol. 29: 340–344, 1958.
 128. Hall, F. G. A spectroscopic method for the study of haemoglobin in dilute solutions. J. Physiol. Lond. 80: 502–507, 1934.
 129. Hall, F. G. Haemoglobin function in the developing chick. J. Physiol. Lond. 83: 222–228, 1935.
 130. Hasaart, T. H. M., and J. de Haan. Depression of uterine blood flow during total umbilical cord occlusion in sheep. Eur. J. Obstet. Gynecol. Reprod. Biol. 19: 125–131, 1985.
 131. Haurowitz, F. Zur Chemie des Blutfarbstoffes. Über das Hämoglobin des Menschen. Z. Phys. Chem. 186: 141–147, 1930.
 132. Hebbel, R. P., E. M. Berger, and J. W. Eaton. Effect of increased maternal hemoglobin oxygen affinity on fetal growth in the rat. Blood 55: 969–974, 1980.
 133. Heerhaber, I., H. H. Loeschcke, and U. Westphal. Eine Wirkung des Progesterons auf die Atmung. Pfluegers Arch. 250: S42–S55, 1948.
 134. Hellegers, A. E., C. J. Heller, R. E. Behrman, and F. C. Battaglia. Oxygen and carbon dioxide transfer across the rhesus monkey placenta (Macaca mulatta). Am. J. Obstet. Gynecol. 88: 22–31, 1964.
 135. Hellegers, A. E., and J. J. P. Schruefer. Nomograms and empirical equations relating oxygen tension, percentage saturation, and pH in maternal and fetal blood. Am. J. Obstet. Gynecol. 81: 377–384, 1961.
 136. Hill, E. P., J. R. Hill, G. G. Power, and L. D. Longo. Carbon monoxide exchanges between the human fetus and mother: a mathematical model. Am. J. Physiol. 232 (Heart Circ. Physiol. 1): H311–H323, 1977.
 137. Hill, E. P., and L. D. Longo. Placental CO2 exchange. In: Biophysics and Physiology of Carbon Dioxide, edited by C. Bauer, G. Gros, and H. Bartels. Berlin: Springer‐Verlag, 1980, p. 379–389.
 138. Hill, E. P., G. G. Power, and L. D. Longo. A mathematical model of placental O2 transfer with consideration of hemoglobin reaction rates. Am. J. Physiol. 222: 721–729, 1972.
 139. Hill, E. P., G. G. Power, and L. D. Longo. A mathematical model of carbon dioxide transfer in the placenta and its interaction with oxygen. Am. J. Physiol. 224: 283–299, 1973.
 140. Hill, E. P., G. G. Power, and L. D. Longo. Mathematical simulation of pulmonary O2 and CO2 exchange. Am. J. Physiol. 224: 904–917, 1973.
 141. Hjelm, M. The mode of expressing the content of intracellular components of human erythrocytes with special reference to adenine nucleotides. Scand. J. Haematol. 6: 56–64, 1969.
 142. Hlastala, M. P., T. A. Standaert, R. L. Franada, and H. P. McKenna. Hemoglobin‐ligand interaction in fetal and maternal sheep blood. Respir. Physiol. 34: 185–194, 1978.
 143. Hollán, S. R., J. G. Szelényi, J. H. Breuer, G. Medgyesi, and V. N. Sötér. Differences between the structure and function of human adult and foetal erythrocytes. Folia Haematol. Leipz. 90: 125–133, 1968.
 144. Holland, R. A. B. Rate of carbon dioxide uptake by suspension of human fetal red cell. In: Fetal and Newborn Cardiovascular Physiology. Fetal and Newborn Circulation, edited by L. D. Longo and D. D. Reneau. New York: Garland, 1978, vol. 2, p. 475–482.
 145. Horan, M. Studies in anaemia of infancy and childhood. The haemoglobin, red cell count, and packed cell volume of normal English infants during the first year of life. Arch. Dis. Child. 25: 110–128, 1950.
 146. Hörlein, H., and G. Weber. Über chronische familiare Methämoglobinamie und eine neue Modifikation des Methämoglobins. Dtsch. Med. Wochenschr. 73: 476–478, 1948.
 147. Howard, R. C., P. D. Bruns, and J. A. Lichty. Studies on babies born at high altitudes. III. Arterial oxygen saturation and hematocrit values at birth. AMA J. Dis. Child. 93: 674–678, 1957.
 148. Huckabee, W. E., and D. H. Barron. Factors affecting the determination of uterine blood flow in vivo. Circ. Res. 9: 312–318, 1961.
 149. Huehns, E. R., and A. M. Farooqui. Oxygen dissociation properties of human embryonic red cells. Nature Lond. 254: 335–337, 1975.
 150. Huehns, E. R., F. V. Flynn, E. A. Butler, and G. H. Beaven. Two new haemoglobin variants in a very young human embryo. Nature Lond. 189: 496–497, 1961.
 151. Huehns, E. R., F. Hecht, J. V. Keil, and A. G. Motulsky. Developmental hemoglobin anomalies in a chromosomal triplication: D1 trisomy syndrome. Proc. Natl. Acad. Sci. USA 51: 89–97, 1964.
 152. Hüfner, C. G. von. Neue Versuche zur Bestimmung der Sauerstoffcapacitat des Blutfarbstoffs. Arch. Physiol. Leipz. 130–176, 1894.
 153. Huggett, A. St. G. Foetal blood‐gas tensions and gas transfusion through the placenta of the goat. J. Physiol. Lond. 62: 373–384, 1927.
 154. Humpeler, E., and H. Amor. Sex differences in the oxygen affinity of hemoglobin. Pfluegers Arch. 343: 151–156, 1973.
 155. Hunter, J. Observations on Certain Parts of the Animal Oeconomy. London: Castle‐Street Leicester‐Square, 1786.
 156. Itskovitz, J., B. W. Goetzman, C. Roman, and A. M. Rudolph. Effects of fetal‐maternal exchange transfusion on fetal oxygenation and blood flow distribution. Am. J. Physiol. 247 (Heart Circ. Physiol. 16): H655–H660, 1984.
 157. Itskovitz, J., E. F. LaGamma, and A. M. Rudolph. The effect of reducing umbilical blood flow on fetal oxygenation. Am. J. Obstet. Gynecol. 145: 813–818, 1983.
 158. Jansen, C. A. M., E. J. Krane, A. L. Thomas, N. F. G. Beck, K. C. Lowe, P. Joyce, M. Parr, and P. W. Nathanielsz. Continuous variability of fetal PO2 in the chronically catheterized fetal sheep. Am. J. Obstet. Gynecol. 134: 776–783, 1979.
 159. Jelkmann, W., and C. Bauer. Oxygen affinity and phosphate compounds of red blood cells during intrauterine development of rabbits. Pfluegers Arch. 372: 149–156, 1977.
 160. Johnson, J. W. C. The diffusivities of oxygen and water in human chorion (Abstract). Soc. Gynecol. Invest. Program Meet., Denver, March 20–21, 1969, p. 15.
 161. Kaiser, I. H., J. N. Cummings, S. R. M. Reynolds, and J. P. Marbarger. Acclimatization response of the pregnant ewe and fetal lamb to diminished ambient pressure. J. Appl. Physiol. 13: 171–178, 1958.
 162. Khazin, A. F., E. H. Hon, and F. W. Hehre. Effects of maternal hyperoxia on the fetus. I. Oxygen tension. Am. J. Obstet. Gynecol. 109: 628–637, 1971.
 163. Kirschbaum, T. H. Fetal hemoglobin composition as a parameter of the oxyhemoglobin dissociation curve of fetal blood. Am. J. Obstet. Gynecol. 84: 477–485, 1962.
 164. Kirschbaum, T. H., C. R. Brinkman III, and N. S. Assali. Effects of maternal‐fetal blood exchange transfusion in fetal lambs. Am. J. Obstet. Gynecol. 110: 190–202, 1971.
 165. Kirschbaum, T. H., and N. Z. Shapiro. A mathematical model of placental oxygen transfer. J. Theor. Biol. 25: 380–402, 1969.
 166. Kleihauer, E. Blutausstrich. Z. Geburtshilfe Gynaekol. 159: 79–86, 1962.
 167. Kleihauer, E., H. Braun, and K. Betke. Demonstration von fetalem Hämoglobin in den Erythrocyten eines Blutaus‐strichs. Klin. Wochenschr. 35: 637–638, 1957.
 168. Klocke, R. A. Oxygen transport and 2,3‐diphosphoglycerate. Chest 62, Suppl.: 79S–85S, 1972.
 169. Koch, H.‐H., and W. Schröter. Kompensatorische Veränderungen der erythrocytären 2,3‐Diphosphoglyceratkionzentration bei Anämien und Polyglobulien. Monatsschr. Kinderheilkd. 121: 392–394, 1973.
 170. Koos, B. J., G. G. Power, and L. D. Longo. Placental oxygen transfer with considerations for maternal exercise. In: Exercise in Pregnancy, edited by R. Artal and R. A. Wiswell. Baltimore, MD: Williams & Wilkins, 1986, p. 155–180.
 171. Körber, E. von. Über Differenzen des Blutfarbstoffes. Dorpat, Germany, 1866. Inaugural dissertation.
 172. Korecký, B., and B. Raška. A contribution to the question of variability in the specific blood capacity for oxygen. Physiol. Bohemoslov. 7: 181–187, 1958.
 173. Krüger, F. von. Beobachtungen über die Absorption des Lichtes durch das Oxyhämoglobin. Z. Biol. 24: 47–66, 1887.
 174. Krüger, F. von. Vergleichende Untersuchungen über die Resistenz das Hämoglobins Verschiedener Tiere. Z. Vgl. Physiol. 2: 254–263, 1925.
 175. Krüger, F. von, and W. Gerlach. Weitere Untersuchungen über den Einfluss von Blutentziehungen auf die Resistenz des Blutfarbstoffes. Z. Gesamte Exp. Med. 54: 653–660, 1927.
 176. Künzel, W., L. J. Mann, A. Bhakthavathsalan, J. Airomlooi, and M. Liu. The effect of umbilical vein occlusion on fetal oxygenation, cardiovascular parameters, and fetal electroencephalogram. Am. J. Obstet. Gynecol. 128: 201–208, 1977.
 177. Künzel, W., and W. Moll. Uterine O2 consumption and blood flow of the pregnant uterus. Experiments in pregnant guinea pigs. Z. Geburtshilfe Perinatol. 176: 108–117, 1972.
 178. Laga, E. M., S. G. Driscoll, and H. N. Munro. Quantitative studies of human placenta. I. Morphometry. Biol. Neonat. 23: 231–259, 1973.
 179. Lambertsen, C. J. Effects of oxygen at high partial pressure. In: Handbook of Physiology. Respiration, edited by W. O. Fenn and H. Rahn. Washington, DC: Am. Physiol. Soc., 1965, sect. 3, vol. II, p. 1027–1046.
 180. Lamport, H. The transport of oxygen in the sheep's placenta: the diffusion constant of the placenta. Yale J. Biol. Med. 27: 26–34, 1954/1955.
 181. Lardner, T. J. A model for placental oxygen exchange. J. Biomech. 8: 131–134, 1975.
 182. Lecks, H., and I. J. Wolman. Fetal hemoglobin in the human: a review. Am. J. Med. Sci. 219: 684–689, 1950.
 183. Lecrone, C. N. Absence of special fetal hemoglobin in beagle dogs. Blood 35: 451–452, 1970.
 184. Leibson, R. G., I. I. Likhnitzky, and M. G. Sax. Oxygen transport of the foetal and maternal blood during pregnancy. J. Physiol. Lond. 87: 97–112, 1936.
 185. Lenfant, C., R. Elsner, G. L. Kooyman, and C. M. Drabek. Respiratory function of blood of the adult and fetus Weddell seal Leptonychotes weddelli. Am. J. Physiol. 216: 1595–1597, 1969.
 186. Levinson, G., S. M. Shnider, A. A. De Lorimier, and J. L. Steffenson. Effects of maternal hyperventilation on uterine blood flow and fetal oxygenation and acid‐base balance. Anesthesiology 40: 340–347, 1974.
 187. Liley, A. W. Intrauterine transfusion of foetus in haemolytic disease. Br. Med. J. 2: 1107–1109, 1963.
 188. Longmuir, I. S., D. C. Martin, H. J. Gold, and S. Sun. Nonclassical respiratory activity of tissue slices. Microvasc. Res. 3: 125–141, 1971.
 189. Longmuir, I. S., and S. Sun. A hypothetical tissue oxygen carrier. Microvasc. Res. 2: 287–293, 1970.
 190. Longo, L. D. Carbon monoxide in the pregnant mother and fetus and its exchange across the placenta. Ann. NY Acad. Sci. 174: 313–341, 1970.
 191. Longo, L. D. Carbon monoxide: effects on oxygenation of the fetus‐in‐utero. Science Wash. DC 194: 523–525, 1976.
 192. Longo, L. D. The biologic effects of carbon monoxide on the pregnant woman, fetus, and newborn infant. Am. J. Obstet. Gynecol. 129: 69–103, 1977.
 193. Longo, L. D., W. W. Allen, J. W. H. Niswonger, K. D. Pagel, H. C. Wieland, and R. D. Gilbert. The interrelations of blood and extracellular fluid volumes and cardiac output in the newborn lamb. In: Fetal and Newborn Cardiovascular Physiology. Developmental Aspects, edited by L. D. Longo and D. D. Reneau. New York: Garland, 1978, vol. 1, p. 345–367.
 194. Longo, L. D., and K. S. Ching. Placental diffusing capacity for carbon monoxide and oxygen in unanesthetized sheep. J. Appl. Physiol. 43: 885–893, 1977.
 195. Longo, L. D., P. S. Dale, and R. D. Gilbert. Uteroplacental O2 uptake: continuous measurements during uterine quiescence and contractions. Am. J. Physiol. 250 (Regulatory Integrative Comp. Physiol. 19): R1099–R1116, 1986.
 196. Longo, L. D., M. Delivoria‐Papadopoulos, and R. E. Forster II. Placental CO2 transfer after fetal carbonic anhydrase inhibition. Am. J. Physiol. 226: 703–710, 1974.
 197. Longo, L. D., M. Delivoria‐Papadopoulos, G. G. Power, E. P. Hill, and R. E. Forster II. Diffusion equilibration of inert gases between maternal and fetal placental capillaries. Am. J. Physiol. 219: 561–569, 1970.
 198. Longo, L. D., and J. S. Hardesty. Maternal blood volume: measurement, hypothesis of control, and clinical considerations. Rev. Perinat. Med. 5: 35–59, 1984.
 199. Longo, L. D., E. P. Hill, and G. G. Power. Factors affecting placental oxygen transfer. In: Chemical Engineering in Medicine, edited by D. D. Reneau. New York: Plenum, 1972, p. 88–129.
 200. Longo, L. D., E. P. Hill, and G. G. Power. Theoretical analysis of factors affecting placental O2 transfer. Am. J. Physiol. 222: 730–739, 1972.
 201. Longo, L. D., and G. G. Power. Analysis of PO2 and PCO2 differences between maternal and fetal blood in the placenta. J. Appl. Physiol. 26: 48–55, 1969.
 202. Longo, L. D., and G. G. Power. Long‐term regulation of fetal cardiac output. A theory on the role of carbon dioxide. Gynecol. Invest. 4: 277–287, 1973.
 203. Longo, L. D., and G. G. Power. Problems in the placental transfer of carbon dioxide. In: The Placenta, Biological and Clinical Aspects, edited by K. S. Moghissi and E. S. E. Hafez. Springfield, IL: Thomas, 1974, p. 89–125.
 204. Longo, L. D., and G. G. Power. Placental oxygen transfer: a systems approach. In: Reviews in Perinatal Medicine, edited by E. M. Scarpelli and E. V. Cosmi. Baltimore, MD: University Park, 1976, vol. I, p. 1–34.
 205. Longo, L. D., G. G. Power, and R. E. Forster II. Respiratory function of the placenta as determined with carbon monoxide in sheep and dogs. J. Clin. Invest. 46: 812–828, 1967.
 206. Longo, L. D., G. G. Power, and R. E. Forster II. Placental diffusing capacity for carbon monoxide at varying partial pressures of oxygen. J. Appl. Physiol. 26: 360–370, 1969.
 207. Lorijn, R. H. W., and L. D. Longo. Clinical and physiological implications of increased fetal oxygen consumption. Am. J. Obstet. Gynecol. 136: 451–457, 1980.
 208. Lorijn, R. H. W., and L. D. Longo. Norepinephrine elevation in the fetal lamb: oxygen consumption and cardiac output. Am. J. Physiol. 239 (Regulatory Integrative Comp. Physiol. 8): R115–R122, 1980.
 209. Lorijn, R. H. W., J. C. Nelson, and L. D. Longo. Induced fetal hyperthyroidism: cardiac output and oxygen consumption. Am. J. Physiol. 239 (Heart Circ. Physiol. 8): H302–H307, 1980.
 210. Lotgering, F. K., R. D. Gilbert, and L. D. Longo. Exercise responses in pregnant sheep: oxygen consumption, uterine blood flow, and blood volume. J. Appl. Physiol. 55: 834–841, 1983.
 211. Lotgering, F. K., R. D. Gilbert, and L. D. Longo. Exercise responses in pregnant sheep: blood gases, temperatures, and fetal cardiovascular system. J. Appl. Physiol. 55: 842–850, 1983.
 212. Low, J. A., R. W. Boston, and F. W. Cervenko. Effect of low maternal carbon dioxide tension on placental gas exchange. Am. J. Obstet. Gynecol. 106: 1032–1043, 1970.
 213. Lucius, H., H. Gahlenbeck, H. O. Kleine, H. Fabel, and H. Bartels. Respiratory functions, buffer system, and electrolyte concentrations of blood during human pregnancy. Respir. Physiol. 9: 311–317, 1970.
 214. Ludwig, K. S. Zur Feinstruktur der maternofetalen Verbindung im Placentom des Schafes (Ovis avies L.). Experientia Basel 18: 212–213, 1962.
 215. Lumley, J., P. Renou, W. Newman, and C. Wood. Hyperventilation in obstetrics. Am. J. Obstet. Gynecol. 103: 847–855, 1969.
 216. Lund, C. J. The recognition and treatment of fetal heart arrhythmias due to anoxia. Am. J. Obstet. Gynecol. 40: 946–957, 1940.
 217. Lye, S. J., M. E. Wlodek, and J. R. G. Challis. Relation between fetal arterial PO2 and oxytocin‐induced uterine contractions in pregnant sheep. Can. J. Physiol. Pharmacol. 62: 1337–1340, 1984.
 218. Madsen, H., and J. Ditzel. Red cell 2,3‐diphosphoglycerate and hemoglobin‐oxygen affinity during normal pregnancy. Acta Obstet. Gynecol. Scand. 63: 399–402, 1984.
 219. Madsen, H., and J. Ditzel. Red cell 2,3‐diphosphoglycerate and hemoglobin‐oxygen affinity during diabetic pregnancy. Acta Obstet. Gynecol. Scand. 63: 403–406, 1984.
 220. Makowski, E. L. Maternal and fetal vascular nets in placentas of sheep and goats. Am. J. Obstet. Gynecol. 100: 283–288, 1968.
 221. Makowski, E. L., F. C. Battaglia, G. Meschia, R. E. Behrman, J. Schruefer, A. E. Seeds, and P. D. Bruns. Effect of maternal exposure to high altitude upon fetal oxygenation. Am. J. Obstet. Gynecol. 100: 852–861, 1968.
 222. Makowski, E. L., R. H. Hertz, and G. Meschia. Effects of acute maternal hypoxia and hyperoxia on the blood flow to the pregnant uterus. Am. J. Obstet. Gynecol. 115: 624–631, 1973.
 223. Makowski, E. L., G. Meschia, W. Droegemueller, and F. C. Battaglia. Distribution of uterine blood flow in the pregnant sheep. Am. J. Obstet. Gynecol. 101: 409–412, 1968.
 224. Martin, C. B., Jr., H. S. McGaughey, Jr., I. H. Kaiser, M. W. Donner, and E. M. Ramsey. Intermittent functioning of the uteroplacental arteries. Am. J. Obstet. Gynecol. 90: 819–823, 1964.
 225. Mathers, N. P., G. B. James, and J. Walker. The oxygen affinity of the blood of infants treated by intrauterine transfusion. J. Obstet. Gynaecol. Br. Commonw. 77: 648–653, 1970.
 226. Mayhew, T. M., C. F. Joy, and J. D. Haas. Structure‐function correlation in the human placenta: the morphometric diffusing capacity for oxygen at full term. J. Anat. 139: 691–708, 1984.
 227. McCarthy, E. F. The oxygen affinity of human maternal and foetal haemoglobin. J. Physiol. Lond. 102: 55–61, 1943.
 228. Merlet‐Bénichou, C., E. Azoulay, and M. Muffat‐Joly. Dependence of 2,3‐DPG and oxygen affinity of haemoglobin on sex and pregnancy in the guinea pig. Pfluegers Arch. 354: 187–195, 1975.
 229. Meschia, G., F. C. Battaglia, and P. D. Bruns. Theoretical and experimental study of transplacental diffusion. J. Appl. Physiol. 22: 1171–1178, 1967.
 230. Meschia, G., F. C. Battaglia, E. L. Makowski, and W. Droegemueller. Effect of varying umbilical blood O2 affinity on umbilical vein Po2. J. Appl. Physiol. 26: 410–416, 1969.
 231. Meschia, G., J. R. Cotter, E. L. Makowski, and D. H. Barron. Simultaneous measurement of uterine and umbilical blood flows and oxygen uptakes. Q. J. Exp. Physiol. 52: 1–18, 1966.
 232. Meschia, G., A. Hellegers, J. N. Blechner, A. S. Wolkoff, and D. H. Barron. A comparison of the oxygen dissociation curves of the bloods of maternal, fetal and newborn sheep at various pHs. Q. J. Exp. Physiol. 46: 95–100, 1961.
 233. Meschia, G., E. L. Makowski, and F. C. Battaglia. The use of uterine and umbilical veins of sheep for a description of fetal acid‐base balance and oxygenation. Yale J. Biol. Med. 42: 154–165, 1969/1970.
 234. Meschia, G., H. Prystowsky, A. Hellegers, W. Hucka‐bee, J. Metcalfe, and D. H. Barron. Observations on the oxygen supply to the fetal llama. Q. J. Exp. Physiol. 45: 284–291, 1960.
 235. Meschia, G., A. S. Wolkoff, and D. H. Barron. The oxygen, carbon dioxide and hydrogen‐ion concentrations in the arterial and uterine venous bloods of pregnant sheep. Q. J. Exp. Physiol. 44: 333–342, 1959.
 236. Metcalfe, J. Uterine oxygen supply and fetal health. Yale J. Biol. Med. 42: 166–179, 1969/1970.
 237. Metcalfe, J., H. Bartels, and W. Moll. Gas exchange in the pregnant uterus. Physiol. Rev. 47: 782–838, 1967.
 238. Metcalfe, J., D. S. Dhindsa, and M. J. Novy. General aspects of oxygen transport in maternal and fetal blood. In: Respiratory Gas Exchange and Blood Flow in the Placenta, edited by L. D. Longo and H. Bartels. Bethesda, MD: Natl. Inst. Health, 1972, p. 63–77. (No. NIH 73‐361.)
 239. Metcalfe, J., G. Meschia, A. Hellegers, H. Prystowsky, W. Huckabee, and D. H. Barron. Observations on the placental exchange of the respiratory gases in pregnant ewes at high altitude. Q. J. Exp. Physiol. 47: 74–92, 1962.
 240. Metcalfe, J., W. Moll, H. Bartels, P. Hilpert, and J. T. Parer. Transfer of carbon monoxide and nitrous oxide in the artificially perfused sheep placenta. Circ. Res. 16: 95–101, 1965.
 241. Metcalfe, J., S. L. Romney, J. R. Swartwout, D. M. Pitcairn, A. N. Lethin, Jr., and D. H. Barron. Uterine blood flow and oxygen consumption in pregnant sheep and goats. Am. J. Physiol. 197: 929–934, 1959.
 242. Miller, F. C., R. H. Petrie, J. J. Arce, R. H. Paul, and E. H. Hon. Hyperventilation during labor. Am. J. Obstet. Gynecol. 120: 489–495, 1974.
 243. Moll, W., and E. Kastendieck. Transfer of N2O, CO and HTO in the artificially perfused guinea‐pig placenta. Respir. Physiol. 29: 283–302, 1977.
 244. Moore, L. G., D. Jahnigen, S. S. Rounds, J. T. Reeves, and R. T. Grover. Maternal hyperventilation helps preserve arterial oxygenation during high‐altitude pregnancy. J. Appl. Physiol. 52: 690–694, 1982.
 245. Moore, L. G., S. S. Rounds, D. Jahnigen, R. F. Grover, and J. T. Reeves. Infant birth weight is related to maternal arterial oxygenation at high altitude. J. Appl. Physiol. 52: 695–699, 1982.
 246. Moore, W. M. O., F. C. Battaglia, and A. E. Hellegers. Whole blood oxygen affinities of women with various hemoglobinopathies. Am. J. Obstet. Gynecol. 97: 63–66, 1967.
 247. Morishima, H. O., F. Moya, A. C. Bossers, and S. S. Daniel. Adverse effects of maternal hypocapnia on the newborn guinea pig. Am. J. Obstet. Gynecol. 88: 524–528, 1964.
 248. Mossman, H. W. The rabbit placenta and the problem of placental transmission. Am. J. Anat. 37: 433–497, 1926.
 249. Motoyama, E. K., G. Rivard, F. Acheson, and C. D. Cook. Adverse effect of maternal hyperventilation on the foetus. Lancet 1: 286–288, 1966.
 250. Motoyama, E. K., G. Rivard, F. Acheson, and C. D. Cook. The effect of changes in maternal pH and Pco2 of fetal lambs. Anesthesiology 28: 891–903, 1967.
 251. Moya, F., H. O. Morishima, S. M. Shnider, and L. S. James. Influence of maternal hyperventilation on the newborn infant. Am. J. Obstet. Gynecol. 91: 76–84, 1965.
 252. Mueggler, P. A., G. Jones, J. S. Peterson, J. M. Bisson‐nette, R. D. Koler, J. Metcalfe, R. T. Jones, and J. A. Black. Postnatal regulation of canine oxygen delivery: erythrocyte components affecting Hb function. Am. J. Physiol. 238 (Heart Circ. Physiol. 7): H73–H79, 1980.
 253. Myers, R. E., E. Mueller‐Heubach, and K. Adamsons. Predictability of the state of fetal oxygenation from a quantitative analysis of the components of late deceleration. Am. J. Obstet. Gynecol. 115: 1083–1094, 1973.
 254. Nelson, P. S., R. D. Gilbert, and L. D. Longo. Fetal growth and placental diffusing capacity in guinea pigs following long‐term maternal exercise. J. Dev. Physiol. Oxf. 5: 1–10, 1983.
 255. Newcomb, S. L., and G. G. Power. Hematocrit of the fetal rabbit placenta. Am. J. Physiol. 229: 1393–1396, 1975.
 256. Newman, W., L. McKinnon, L. Phillips, P. Paterson, and C. Wood. Oxygen transfer from mother to fetus during labor. Am. J. Obstet. Gynecol. 99: 61–70, 1967.
 257. Novy, M. J. Alterations in blood oxygen affinity during fetal and neonatal life. In: Oxygen Affinity of Hemoglobin and Red Cell Acid Base Status, edited by M. Rørth and P. Astrup. Copenhagen: Munksgaard, 1972, p. 696–712. (Alfred Benzon Symp. 4.)
 258. Novy, M. J., F. D. Frigoletto, C. L. Easterday, I. Uman‐sky, and N. M. Nelson. Changes in umbilical‐cord blood oxygen affinity after intrauterine transfusions for erythroblastosis. N. Engl. J. Med. 285: 589–596, 1971.
 259. Novy, M. J., A. S. Hoversland, D. S. Dhindsa, and J. Metcalfe. Blood oxygen affinity and hemoglobin type in adult, newborn, and fetal pigs. Respir. Physiol. 19: 1–11, 1973.
 260. Novy, M. J., and J. T. Parer. Absence of high blood oxygen affinity in the fetal cat. Respir. Physiol. 6: 144–150, 1969.
 261. Novy, M. J., E. N. Peterson, and J. Metcalfe. Respiratory characteristics of maternal and fetal blood in cyanotic congenital heart disease. Am. J. Obstet. Gynecol. 100: 821–828, 1968.
 262. Orzalesi, M. M., and W. W. Hay. The regulation of oxygen affinity of fetal blood. I. In vitro experiments and results in normal infants. Pediatrics 48: 857–864, 1971.
 263. Oski, F. A. Hematological problems. In: Neonatology. Pathophysiology and Management of the Newborn, edited by G. B. Avery. Philadelphia, PA: Lippincott, 1975, p. 379–422.
 264. Parer, J. T. Oxygen transport in human subjects with hemoglobin variants having altered oxygen affinity. Respir. Physiol. 9: 43–49, 1970.
 265. Parer, J. T., and R. E. Behrman. The oxygen consumption of the pregnant uterus and fetus of Macaca mulatta. Respir. Physiol. 3: 288–301, 1967.
 266. Parer, J. T., M. Eng, H. Aoba, and K. Ueland. Uterine blood flow and oxygen uptake during maternal hyperventilation in monkeys at cesarean section. Anesthesiology 32: 130–135, 1970.
 267. Parker, H. R., and M. J. Purves. Some effects of maternal hyperoxia and hypoxia on the blood gas tensions and vascular pressures in the foetal sheep. Q. J. Exp. Physiol. 52: 205–221, 1967.
 268. Paton, J. B., E. Peterson, D. E. Fisher, and R. E. Behrman. Oxygen dissociation curves of fetal and adult baboons. Respir. Physiol. 12: 283–290, 1971.
 269. Peng, A. T. C., L. S. Blancato, and E. K. Motoyama. Effect of maternal hypocapnia vs. eucapnia on the foetus during caesarean section. Br. J. Anaesth. 44: 1173–1178, 1972.
 270. Perk, K., and D. Danon. Comparative structure analysis of foetal and adult type red cells in newborn and adult cattle. Res. Vet. Sci. 6: 442–446, 1965.
 271. Permutt, S., and R. L. Riley. Hemodynamics of collapsible vessels with tone: the vascular waterfall. J. Appl. Physiol. 18: 924–932, 1963.
 272. Power, G. G. Some aspects of O2 and CO2 transfer in the placenta. Chest 61, Suppl.: 22S–24S, 1972.
 273. Power, G. G., P. S. Dale, and P. S. Nelson. Distribution of maternal and fetal blood flow within cotyledons of the sheep placenta. Am. J. Physiol. 241 (Heart Circ. Physiol. 10): H486–H496, 1981.
 274. Power, G. G., and R. D. Gilbert. Umbilical vascular compliance in sheep. Am. J. Physiol. 233 (Heart Circ. Physiol. 2): H660–H664, 1977.
 275. Power, G. G., E. P. Hill, and L. D. Longo. Analysis of uneven distribution of diffusing capacity and blood flow in the placenta. Am. J. Physiol. 222: 740–746, 1972.
 276. Power, G. G., and F. Jenkins. Factors affecting O2 transfer in sheep and rabbit placenta perfused in situ. Am. J. Physiol. 229: 1147–1153, 1975.
 277. Power, G. G., and L. D. Longo. Graphical analysis of maternal and fetal exchange of O2 and CO2. J. Appl. Physiol. 26: 38–47, 1969.
 278. Power, G. G., and L. D. Longo. Sluice flow in placenta: maternal vascular pressure effects on fetal circulation. Am. J. Physiol. 225: 1490–1496, 1973.
 279. Power, G. G., L. D. Longo, H. N. Wagner, Jr., D. E. Kuhl, and R. E. Forster II. Uneven distribution of maternal and fetal placental blood flow, as demonstrated using macroaggregates, and its response to hypoxia. J. Clin. Invest. 46: 2053–2063, 1967.
 280. Pritchard, J. A. Changes in the blood volume during pregnancy and delivery. Anesthesiology 26: 393–399, 1965.
 281. Pritchard, J. A., and C. F. Hunt. A comparison of the hematologic responses following the routine prenatal administration of intramuscular and oral iron. Surg. Gynecol. Obstet. 106: 516–518, 1958.
 282. Prystowsky, H. Fetal blood studies. VII. The oxygen pressure gradient between the maternal and fetal bloods of the human in normal and abnormal pregnancy. Bull. Johns Hopkins Hosp. 101: 48–56, 1957.
 283. Prystowsky, H., A. Hellegers, and P. Bruns. Fetal blood studies. XIV. A comparative study of the oxygen dissociation curve of nonpregnant, pregnant, and fetal human blood. Am. J. Obstet. Gynecol. 78: 489–493, 1959.
 284. Prystowsky, H., A. Hellegers, and P. Bruns. Fetal blood studies. XV. The carbon dioxide concentration gradient between the fetal and maternal blood of humans. Am. J. Obstet. Gynecol. 81: 372–376, 1961.
 285. Prystowsky, H., A. Hellegers, G. Meschia, J. Metcalfe, W. Huckabee, and D. H. Barron. The blood volume of fetuses carried by ewes at high altitude. Q. J. Exp. Physiol. 45: 292–297, 1960.
 286. Qvist, J., R. E. Weber, and W. M. Zapol. Oxygen equilibrium properties of blood and hemoglobin of fetal and adult Weddell seals. J. Appl. Physiol. 50: 999–1005, 1981.
 287. Ramsey, E. M. Uteroplacental circulation during labor. Clin. Obstet. Gynecol. 11: 78–95, 1968.
 288. Ramsey, E. M., G. W. Corner, Jr., and M. W. Donner. Cineradioangiographic visualization of the venous drainage of the primate placenta in vivo. Science Wash. DC 141: 909–910, 1963.
 289. Ramsey, E. M., G. W. Corner, Jr., M. W. Donner, and H. M. Stran. Radioangiographic studies of circulation in the maternal placenta of the rhesus monkey: preliminary report. Proc. Natl. Acad. Sci. USA 46: 1003–1008, 1960.
 290. Ramsey, E. M., C. B. Martin, Jr., H. S. McGaughey, Jr., I. H. Kaiser, and M. W. Donner. Venous drainage of the placenta in rhesus monkeys: radiographic studies. Am. J. Obstet. Gynecol. 95: 948–955, 1966.
 291. Rankin, J., G. Meschia, E. L. Makowski, and F. C. Battaglia. Macroscopic distribution of blood flow in the sheep placenta. Am. J. Physiol. 219: 9–16, 1970.
 292. Rankin, J. H. G., and E. N. Peterson. Application of the theory of heat exchangers to a physiological study of the goat placenta. Circ. Res. 24: 235–250, 1969.
 293. Reimann, F., and E. Yenen. Der Einfluss von fetalem Hämoglobin auf die Bestimmung der osmotischen Resistenz im Blut des Neugeborenen. Acta Haematol. Basel 27: 359–366, 1962.
 294. Riegel, K., H. Bartels, I. O. Buss, P. G. Wright, E. Kleihauer, C. P. Luck, J. T. Parer, and J. Metcalfe. Comparative studies of the respiratory functions of mammalian blood. IV. Fetal and adult African elephant blood. Respir. Physiol. 2: 182–195, 1967.
 295. Riegel, K., H. Bartels, D. el Yassin, J. Oufi, E. Kleihauer, J. T. Parer, and J. Metcalfe. Comparative studies of the respiratory functions of mammalian blood. III. Fetal and adult dromedary camel blood. Respir. Physiol. 2: 173–181, 1967.
 296. Rivard, G., E. K. Motoyama, F. M. Acheson, C. D. Cook, and E. O. R. Reynolds. The relation between maternal and fetal oxygen tensions in sheep. Am. J. Obstet. Gynecol. 97: 925–930, 1967.
 297. Rocco, E., T. R. Bennett, and G. G. Power. Placental diffusing capacity in unanesthetized rabbits. Am. J. Physiol. 228: 465–469, 1975.
 298. Roos, J., and C. Romijn. The oxygen dissociation curve of the cow's blood during pregnancy and the dissociation curve of the blood of the newborn animal in the course of the first time after birth. Proc. K. Ned. Akad. Wet. Ser. C Biol. Med. Sci. 40: 803–812, 1937.
 299. Roos, J., and C. Romijn. Some conditions of foetal respiration in the cow. J. Physiol. Lond. 92: 249–267, 1938.
 300. Rooth, G., and S. Sjöstedt. The placental transfer of gases and fixed acids. Arch. Dis. Child. 37: 366–370, 1962.
 301. Rorke, M. J., D. A. Davey, and H. G. Dutoit. Foetal oxygenation during caesarean section. Anaesthesia 23: 585–596, 1968.
 302. Rørth, M., and N. E. Bille‐Brahe. 2,3‐Diphosphoglycerate and creatinine in the red cell during human pregnancy. Scand. J. Clin. Lab. Invest. 28: 271–276, 1971.
 303. Rørth, M., and N. E. Bille‐Brahe. 2,3‐DPG in human pregnancy. In: Oxygen Affinity of Hemoglobin and Red Cell Acid Base Status, edited by M. Rørth and P. Astrup. Copenhagen: Munksgaard, 1972, p. 692–695. (Alfred Benzon Symp. 4.)
 304. Rosenfeld, C. R., F. H. Morriss, Jr., E. L. Makowski, G. Meschia, and F. C. Battaglia. Circulatory changes in the reproductive tissues of ewes during pregnancy. Gynecol. Invest. 5: 252–268, 1974.
 305. Ross, B. B. Comparative properties of the lungs and the placenta: a graphical analysis of placental gas exchange. In: Development of the Lung, edited by A. V. S. de Reuck and R. Porter. Boston, MA: Little, Brown, 1967, p. 238–257. (Ciba Found. Symp.)
 306. Rottino, A., and J. W. Angers. Electrophoretic mobility of the red blood cell during human pregnancy. Am. J. Obstet. Gynecol. 82: 1302–1306, 1961.
 307. Rudolph, A. M., and M. A. Heymann. The circulation of the fetus in utero. Methods for studying distribution of blood flow, cardiac output and organ blood flow. Circ. Res. 21: 163–184, 1967.
 308. Scherrer, M., and H. Bachofen. The oxygen‐combining capacity of hemoglobin (Letter to the editor). Anesthesiology 36: 190, 1972.
 309. Schröder, H., W. Paul, and H.‐P. Leichtweiss. Vascular volumes in isolated perfused guinea pig placenta. Am. J. Physiol. 241 (Heart Circ. Physiol. 10): H73–H77, 1981.
 310. Schroeder, W. A., J. T. Cua, G. Matsuda, and W. D. Fenninger. Hemoglobin F1; an acetyl‐containing hemoglobin. Biochim. Biophys. Acta 63: 532–534, 1962.
 311. Schroeder, W. A., T. H. J. Huisman, J. R. Shelton, J. B. Shelton, E. F. Kleihauer, A. M. Dozy, and B. Robberson. Evidence for multiple structural genes for the γ chain of human fetal hemoglobin. Proc. Natl. Acad. Sci. USA 60: 537–544, 1968.
 312. Schroeder, W. A., J. R. Shelton, J. B. Shelton, and J. Cormick. The amino acid sequence of the α chain of human fetal hemoglobin. Biochemistry 2: 1353–1357, 1963.
 313. Schroeder, W. A., J. R. Shelton, J. B. Shelton, J. Cormick, and R. T. Jones. The amino acid sequence of the γ chain of human fetal hemoglobin. Biochemistry 2: 992–1008, 1963.
 314. Sinet, M., E. Azoulay, and M. C. Blayo. Affinité du sang pour l'oxygèn et 2,3‐DPG chez l'homme, la femme et la femme enciente. Bull. Physio‐Pathol. Respir. 10: 419–434, 1974.
 315. Smellie, W. A Treatise on the Theory and Practice of Midwifery. London: Wilson, 1752, p. 140.
 316. Smith, A. D., R. D. Gilbert, R. J. Lammers, and L. D. Longo. Placental exchange area in guinea pigs following longterm maternal exercise: a stereological analysis. J. Dev. Physiol. Oxf. 5: 11–21, 1983.
 317. Smith, R. C., G. J. Garbutt, R. E. Isaaks, and D. R. Harkness. Oxygen binding of fetal and adult bovine hemoglobin in the presence of organic phosphates and uric acid ribose. Hemoglobin 3: 47–55, 1979.
 318. Sobrevilla, L. A., M. T. Cassinelli, A. Carcelen, and J. M. Malaga. Human fetal and maternal oxygen tension and acid‐base status during delivery at high altitude. Am. J. Obstet. Gynecol. 111: 1111–1118, 1971.
 319. Stenger, V., D. Eitzman, T. Anderson, C. De Padua, I. Gessner, and H. Prystowsky. Observations on the placental exchange of the respiratory gases in pregnant women at cesarean section. Am. J. Obstet. Gynecol. 88: 45–47, 1964.
 320. Stockell, A., M. F. Perutz, H. Muirhead, and S. C. Glauser. A comparison of adult and foetal horse haemoglobins. J. Mol. Biol. 3: 112–116, 1961.
 321. Swenson, E. R., and T. H. Maren. A quantitative analysis of CO2 transport at rest and during maximal exercise. Respir. Physiol. 35: 129–159, 1978.
 322. Swierczewski, E., and A. Minkowski. Le pouvoir oxyphorique (ou capacité en oxyène) du sang artériel foetal. Etud. Neo‐Natales 5: 11–17, 1956.
 323. Tafani, A. La circulation dans le placenta de quelques mammiferes. Arch. Ital. Biol. 8: 49–57, 1887.
 324. Takenaka, O., and H. Morimoto. Oxygen equilibrium characteristics of adult and fetal hemoglobin of Japanese monkey (Macaca fuscata). Biochim. Biophys. Acta 446: 457–462, 1976.
 325. Tautz, C., and E. Kleihauer. Gibt es ein fetales Hämoglobin beim Schwein? II. Analysen des Globins. Res. Exp. Med. 159: 44–49, 1972.
 326. Thornburg, K. L., J. M. Bissonnette, and J. J. Faber. Absence of fetal placental waterfall phenomenon in chronically prepared fetal lambs. Am. J. Physiol. 230: 886–892, 1976.
 327. Torrance, J., P. Jacobs, A. Restrepo, J. Eschbach, C. Lenfant, and C. A. Finch. Intraerythrocytic adaptation to anemia. N. Engl. J. Med. 283: 165–169, 1970.
 328. Tremblay, P. C., S. Sybulski, and G. B. Maughan. Role of the placenta in fetal malnutrition. Am. J. Obstet. Gynecol. 91: 597–605, 1965.
 329. Tweeddale, P. M. Blood oxygen affinities of the adult and foetal large white pig. Respir. Physiol. 19: 145–152, 1973.
 330. Tweeddale, P. M. DPG and the oxygen affinity of maternal and foetal pig blood and haemoglobins. Respir. Physiol. 19: 12–18, 1973.
 331. Tyuma, I., and K. Shimizu. Different response to organic phosphates of human fetal and adult hemoglobins. Arch. Biochem. Biophys. 129: 404–405, 1969.
 332. Valeri, C. R., and N. L. Fortier. Red‐cell 2,3‐diphosphoglycerate and creatine levels in patients with red‐cell mass deficits or with cardiopulmonary insufficiency. N. Engl. J. Med. 281: 1452–1455, 1969.
 333. Versmold, H., and K. P. Riegel. The effect of methemoglobin on the equilibrium between oxygen and the hemoglobins F and A1 at different concentrations of 2,3‐diphosphoglycerate (Abstract). Pediatr. Res. 8: 140, 1974.
 334. Versmold, H., G. Seifert, and K. P. Riegel. Blood oxygen affinity in infancy: the interaction of fetal and adult hemoglobin, oxygen capacity, and red cell hydrogen ion and 2,3‐diphosphoglycerate concentration. Respir. Physiol. 18: 14–25, 1973.
 335. Wagner, P. D. Diffusion and chemical reaction in pulmonary gas exchange. Physiol. Rev. 57: 257–312, 1977.
 336. Wakulenko, J. L. Zur Frage nach der Zusammensetzung und den Eigenschaften des Nabelvenenblutes im Momente der Geburt. Arb. Med. Chem. Lab. K. Univ. Tomsk 2: 1, 1910.
 337. Walker, J., and E. P. N. Turnbull. Haemoglobin and red cells in the human foetus and their relation to the oxygen content of the blood in the vessels of the umbilical cord. Lancet 2: 312–318, 1953.
 338. Waters, R. M., and J. W. Harris. Carbon dioxide and oxygen problems in obstetric anesthesia. Anesth. Analg. 10: 59–63, 1931.
 339. Wells, R. M. G. Haemoglobin‐oxygen affinity in developing embryonic erythroid cells of the mouse. J. Comp. Physiol. 129: 333–338, 1979.
 340. Widness, J. A., H. C. Schwartz, C. B. Kahn, W. Oh, and R. Schwartz. Glycohemoglobin in diabetic pregnancy: a sequential study. Am. J. Obstet. Gynecol. 136: 1024–1029, 1980.
 341. Widness, J. A., H. C. Schwartz, D. Thompson, C. B. Kahn, W. Oh, and R. Schwartz. Haemoglobin A1c (glycohaemoglobin) in diabetic pregnancy: an indicator of glucose control and foetal size. Br. J. Obstet. Gynaecol. 85: 812–817, 1978.
 342. Wilbur, W. J., G. G. Power, and L. D. Longo. Water exchange in the placenta: a mathematical model. Am. J. Physiol. 235 (Regulatory Integrative Comp. Physiol. 4): R181–R199, 1978.
 343. Wilkening, R. B., S. Anderson, L. Martensson, and G. Meschia. Placental transfer as a function of uterine blood flow. Am. J. Physiol. 242 (Heart Circ. Physiol. 11): H429–H436, 1982.
 344. Wilkening, R. B., and G. Meschia. Fetal oxygen uptake, oxygenation, and acid‐base balance as a function of uterine blood flow. Am. J. Physiol. 244 (Heart Circ. Physiol. 13): H749–H755, 1983.
 345. Windle, W. F. Physiology of the Fetus. Origin and Extent of Function in Prenatal Life. Philadelphia, PA: Saunders, 1940.
 346. Winick, M., A. Coscia, and A. Noble. Cellular growth in human placenta. I. Normal placental growth. Pediatrics 39: 248–251, 1967.
 347. Wintrobe, M. M., and H. B. Schumacker, Jr. Comparison of hematopoiesis in the fetus and during recovery from pernicious anemia. Together with a consideration of the relationship of fetal hematopoiesis to macrocytic anemia of pregnancy and anemia in infants. J. Clin. Invest. 14: 837–852, 1935.
 348. Wintrobe, M. M., and H. B. Shumacker, Jr. Erythrocyte studies in the mammalian fetus and newborn. Erythrocyte counts, hemoglobin and volume of packed red corpuscles, mean corpuscular volume, diameter and hemoglobin content, and proportion of miniature red cells in the blood of fetuses and newborn of the pig, rabbit, cat, dog, and man. Am. J. Anat. 58: 313–328, 1936.
 349. Wood, W. G., C. Bunch, S. Kelly, Y. Gunn, and G. Breckon. Control of haemoglobin switching by a developmental clock? Nature Lond. 313: 320–323, 1985.
 350. Wulf, H. Der Gasaustausch in der reifen Placenta des Menschen. Z. Geburtshilfe Gynaekol. 158: 117–134, 1962.
 351. Wynn, R. M., M. Panigel, and A. H. MacLennan. Fine structure of the placenta and fetal membranes of the baboon. Am. J. Obstet. Gynecol. 109: 638–648, 1971.
 352. Young, D. C., R. Popat, E. R. Luther, K. E. Scott, and W. D. R. Writer. Influence of maternal oxygen administration of the term fetus before labor. Am. J. Obstet. Gynecol. 136: 321–324, 1980.
 353. Zacharian, P. K., Q. P. Lee, K. G. Symms, and M. R. Juchau. Further studies on the properties of human placental microsomal cytochrome P‐450. Biochem. Pharmacol. 25: 793–800, 1976.

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Article Title: Respiratory Gas Exchange in the Placenta
 

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Lawrence D. Longo. Respiratory Gas Exchange in the Placenta. Compr Physiol 2011, Supplement 13: Handbook of Physiology, The Respiratory System, Gas Exchange: 351-401. First published in print 1987. doi: 10.1002/cphy.cp030418