Figure 2. Placental transport capacity and uterine extraction efficiency for oxygen and glucose. Placental transport capacity for oxygen (A) and glucose (B) are presented by placental weights for independent group means from previously reported cohorts of thermoneutral and heat stressed ewes during gestation. Placental transport capacity is the net umbilical (fetal) uptake (µmol/min) divided by the maternal arterial-fetal arterial plasma concentration difference (µmol/ml) according to the equation: transport capacity = uptake/concentration difference. Linear regression analysis shows a positive association for placental transport capacity and placental mass (R2). Uterine extraction of oxygen was calculated by expressing the whole blood arterial-venous oxygen concentration difference across the uterine circulation as a percent of the arterial concentration (C). Uterine extraction of glucose was expressed as the plasma arterial-venous concentration difference as a percent of the arterial glucose concentration (D). Group means for thermoneutral control (fill symbols) and heat stressed animals (open symbols) were reported in Bell et al., 1987 (downward triangle); Thureen et al., 1992 (hexagon); Ross et al., 1996 (diamond); Anderson et al., 1997 (small circle, panel A); Regnault et al., 2003 (large circle, panel A); Limesand et al., 2004 (circle, panel B); de Vrijer et al., 2004 (triangle); Limesand et al., 2007 (large square, panel B) and Brown et al., 2012 (small square, panel B). An ANOVA with reported study as the repeated measure identify group (control and heat stress) differences (P-values) for panels C and D.