Continuous Glucose Profiles in Obese and Normal-Weight Pregnant Women on a Controlled Diet

Abstract

Higher rates of macrosomia and large for gestational age are observed among newborns of obese nondiabetic mothers with presumably normal glucose tolerance (NGT). These adverse neonatal outcomes are similar to those observed in women with gestational diabetes. There is continuing debate over what constitutes NGT in pregnancy and whether obese and normal-weight women would have similar glycemic patterns if their respective diets were controlled. The aim of this prospective study was to determine whether (1) glycemic profiles differ between obese and normal-weight women who have NGT; and (2) glycemic profiles in obese women both early and late in gestation are influenced by a controlled diet. Continuous glucose monitoring was used to define 24-hour glycemia among 22 normal-weight and 16 obese pregnant women on an ad libitum and controlled diet. Measurements of glycemia occurred in early (15.7 ± 0.3 weeks) and late (27.7 ± 0.3 weeks) gestation. Fasting blood glucose, nonesterified fatty acids (FFAs), and insulin were also measured both in early and late gestation; however, triglycerides were measured only in early gestation. The 24-hour glucose area under the curve was significantly higher in obese women than in normal-weight women, despite controlled diets both in early (P < 0.05) and late (P < 0.01) pregnancy. Compared with normal-weight women, nearly all fasting and postprandial glycemic parameters, as well as insulin, triglycerides, and FFAs were higher in the obese women late in pregnancy. The percentage body fat was significantly higher in infants born to obese mothers than in those born to normal-weight mothers (9.2% ± 0.5% vs. 7.3% ± 0.4%, P < 0.01). Early maternal body mass index (r, 0.54, P = 0.01), as well as late mean daytime glucose (r, 0.48; P < 0.05), and late fasting insulin (r, 0.49; P < 0.05) correlated with infant percentage body fat in glucose tolerant women. The strongest correlates with infant adiposity were early fasting triglycerides (r, 0.67, P < 0.001) and late fasting FFAs (r, 0.54, P < 0.01). These findings demonstrate that the glycemic profiles of obese pregnant women without diabetes are higher than those of normal-weight women when diet is tightly controlled. Late fasting FFAs, insulin, and mean daytime glucose are highly correlated with infant adiposity, independent of maternal body mass index, but the strongest predictor is early triglycerides. The data suggest the need for study of new management strategies in obese pregnant women with NGT.