THE IMPACT OF GESTATIONAL-AGE AND FETAL GROWTH ON THE MATERNAL-FETAL GLUCOSE-CONCENTRATION DIFFERENCE

Objective: To test whether the human fetus accommodates to the increas ing glucose requirements of late pregnancy with an increased maternal- fetal glucose concentration gradient and whether there are differences in pregnancies with fetal growth restriction (FGR) according to clini cal severity. Methods: Umbilical venous glucose concentration was meas ured in 77 normal pregnancies (appropriate for gestational age [AGA]) and 42 pregnancies complicated by FGR at the time of fetal blood sampl ing. In 40 AGA and in all FGR cases, a maternal ''arterialized'' blood sample was collected simultaneously. Growth-restricted fetuses were s ubdivided into three groups according to fetal heart rate (FHR) record ings and Doppler measurements of the umbilical artery pulsatility inde x (PI): group 1 (normal FHR and PI; 12 cases), group 2 (normal FHR, ab normal PI; 17 cases) and group 3 (abnormal FHR and PI; 13 cases). Resu lts: In normal pregnancies with increasing gestational age, there was a significant decrease (P < .001) of umbilical venous glucose concentr ation and a significant increase of the maternal-fetal glucose concent ration difference (P < .001). In addition, there was a significant rel ation between fetal and maternal glucose concentrations (P < .001). In FGR pregnancies, the maternal-fetal glucose concentration difference was significantly higher in fetuses of groups 2 and 3 compared with no rmal pregnancies and FGR pregnancies of group 1. Conclusion: In human pregnancy, the fetal glucose concentration is a function of both gesta tional age and the maternal glucose concentration. In FGR pregnancies, as an accommodation of the fetus to a restricted placental size and p lacental glucose transport capacity, the maternal-fetal glucose concen tration difference is increased, and this increase is a function of th e clinical severity.