To examine the association between maternal and fetal glucose levels and fetal adiposity and infant birthweight. This is a prospective study of 479 healthy, non-diabetic mother and infant pairs attending the National Maternity Hospital in Ireland. Fasting glucose was measured in early pregnancy (11.8±2.3 weeks). At 28 weeks gestation a repeat fasting glucose was measured and 1h glucose challenge testing (1h GCT) was performed. At 34 weeks' gestation (33+5-34+5 weeks) fetal growth and fetal anterior abdominal wall width, a marker of fetal adiposity, were measured. At delivery cord glucose was measured and neonatal anthropometry recorded. There was a positive correlation between fasting glucose concentration during pregnancy and both infant birthweight and fetal anterior abdominal wall width at 34 weeks gestation. The incidence of macrosomia (birthweight>4.5kg) was significantly greater for maternal and cord blood glucose levels in the highest quartile compared to the lowest quartile (20.7% vs. 11.7%, p<0.05 in the first trimester, 21.3% vs. 7.2%, p<0.05, at 28 weeks, and 33.3% vs. 10%, p<0.05, in cord blood). Maternal glucose concentrations at each time point, though not cord glucose, were related to early pregnancy maternal body mass index (r=0.19, p<0.001 in first trimester, r=0.25, p<0.001 at 28 weeks, r=0.15, p<0.01 with 1h GCT). Maternal glucose homeostasis is an important determinant of fetal size. We have shown that even small variations in fasting glucose concentrations can influence fetal growth and adiposity. This effect is seen from the first trimester and maintained until delivery.
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