Introduction: Fetal glucose is thought to originate from maternal glucose driven across the placenta by a maternal-fetal glucose gradient. Still, there is no correlation between the mass of glucose taken up by the uteroplacenta and the fetal uptake. We propose a hypothesis that the uteroplacenta's own treatment of glucose affects the net mass of glucose taken up by the fetus, independent of the maternal-fetal gradient.
Methods: We performed a human in vivo study of term uncomplicated pregnancies including seventy healthy women delivered by scheduled cesarean delivery. We measured uterine and umbilical blood flow by Doppler ultrasonography, and glucose concentrations in the maternal radial artery, uterine vein, umbilical artery and vein. We calculated Spearman's correlations between uteroplacental and fetal glucose uptake within tertiles of placental glucose consumption.
Results: There were significant correlations between uteroplacental uptake and fetal uptake of glucose when determined within each tertile (Spearman's rho 0.76, (p < 0.001); 0.94 (p < 0.001) and 0.49 (p = 0.029) from lowest to highest tertile, respectively). The median (Q1, Q3) uteroplacental glucose consumption in each tertile was -88.8 (-140.3, 56.7), 29.7 (9.2, 47.4) and 174.7 (87.8, 226.1) (μmol/min). The corresponding median (Q1, Q3) fetal glucose uptake was 152.9 (94.2, 162.7), 110.8 (54.7, 167.2) and 66.6 (8.5, 122.1) (μmol/min).
Discussion: The maternal fetal glucose gradients were similar in the tertiles of placental glucose consumption. Still, the net mass of glucose taken up by the fetus was markedly different between the tertiles. Placental treatment of glucose exhibited a large variation from apparent production to consumption.
Keywords: Fetal glucose uptake; Human pregnancies; Maternal-fetal gradient; Placental glucose transfer; Placental metabolism.
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