Loren Ekind-Hirsch
Objective: We prospectively evaluated differences in fasting- and oral glucose tolerance test (OGTT)-derived indices of insulin action in Caucasian (Cau) and African-American (AA) pregnant women and compared them with obstetric outcomes.
Study design: IRB-approved prospective study in 171 pregnant women undergoing a 3-h OGTT. Mathematical modeling was used to evaluate insulin response, insulin activity and glucose tolerance in fasting and postglucose ingestion state. Insulin sensitivity indices derived from fasting (HOMA-IR) and glucose-stimulated values (SIOGTT) were compared. An insulin sensitivity-secretion index (IS-SI) was calculated from the product of the SIOGTT and early-phase insulin secretion.
Results: Forty-nine patients had gestational diabetes (GDM), 28 had gestational impaired glucose tolerance (GIGT) and 94 had normal glucose tolerance after an abnormal glucose challenge test (NGT-abnGCT). Insulin sensitivity was lowest in women with GDM. In all groups, pregnant AA women were significantly more insulin resistant than Cau women, based on both HOMA-IR and SIOGTT, but had enhanced insulin secretion compared to their Cau counterparts. The mean IS-SI progressively improved for all women from GDM to GIGT to NGT-abnGCT. Women with NGT-abnGCT had a higher prevalence of large-for-gestational age (LGA) newborns and significantly higher cesarean section rate.
Discussion: Insulin measures along with glucose determinations during OGTT testing in pregnant women at risk for diabetes provide valuable information that varies according to race. We observed that pregnant women with a lesser degree of glucose tolerance abnormality during pregnancy who receive no intervention have a higher risk for LGA infants and significantly increased C-section rate (ClinicalTrials.gov number, NCT006874791).