Gestational Diabetes: Glycemic Control in the Last Two Weeks Before Delivery Contributes to Newborn Insulinemia

Fetal hyperinsulinemia in gestational diabetes mellitus (GDM) not only is important during intrauterine life, a time when it can result in macrosomia, but also at delivery, since it can result in neonatal hypoglycemia and hyperbilirubinemia. The question is, how long before delivery does maternal glycemic control contribute to newborn insulinemia in GDM?

In 72 women with GDM, we calculated Spearman's rank (r_s) correlations between umbilical cord blood C-peptide at birth (a biomarker of insulin secretion), and both maternal glycosylated hemoglobin (HbA1c) and mean blood glucose (MBG) recorded in the last two visits prior to delivery. Iterative correlations were done between umbilical cord blood C-peptide at birth, and maternal glucose control, at 0, 1, 2, 3, 4, and 5 weeks before delivery.

At an early visit (32.95 ± 1.8 weeks), r_s = 0.353 (P = 0.07) between HbA1c and C-peptide, whereas r_s = 0.244 (P = 0.186) between MBG and C-peptide. At the latest visit (35.04 ± 1.6 weeks), r_s = 0.456 (P = 0.004) between HbA1c versus C-peptide, and r_s = 0.359 (P = 0.023) between MBG versus C-peptide. Iterative correlations between MBG and C-peptide became significant at 2 weeks before delivery.

To further reduce the risk of hypoglycemia and hyperbilirubinemia in infants born to women with GDM, besides applying a strict in-patient glucose control protocol at delivery, it is necessary to improve even more the quality of maternal glucose control during the last 2 weeks prior to delivery.