Study measurements occurred at 15.7 ± 0.3 weeks’ (early) and 27.7 ± 0.3 weeks’ (late) gestation. depicts maternal demographics, fasting plasma measures, and size-related infant outcomes. Of 50 subjects initially enrolled, 12 did not complete the study because of the demands of the study (n = 4), an early (n = 1) or late (n = 2) diagnosis of gestational diabetes, lack of completion of both study phases (n = 3), incomplete newborn data (n = 1), and the development of systemic lupus erythematosus (n = 1). There were no differences between groups in maternal weight gain or FBG. Fasting insulin, C-peptide, and FFAs were higher in obese compared with normal-weight women, both early and late in pregnancy. Triglycerides were not a primary metabolic variable in the study, as designed, and only were measured early to ensure that subjects were not at risk for triglyceride-induced pancreatitis. However, triglycerides were significantly higher in the obese mothers (P < 0.001). Birth weight, gestational age, and infant macrosomia were not statistically different between the offspring of both groups. However, percentage body fat was significantly higher in the offspring of obese compared with normal-weight subjects, as were measurements of the triceps, subscapular, and the sum of both skinfolds.
Maternal and infant characteristics
The diets consumed by subjects and the effects of diet on glycemia are shown in . Most glucose parameters were not different between the ad libitum and control diets in the normal-weight and obese women both early (not shown) and later in pregnancy. Of interest, there were no significant differences in either the total calories ingested or the percentage of fat or carbohydrate between the ad libitum and control diets both early and late in pregnancy. Given the lack of appreciable effect of the ad libitum versus control diet on glycemic parameters, all comparisons between the groups were subsequently analyzed on the control diet.
CGMS data and macronutrient intake in normal-weight and obese subjects late in pregnancy on control and ad libitum diets
depicts CGMS parameters in normal-weight and obese women during the control diet early () and late () pregnancy. The 24-h AUC glucose, daytime AUC, nocturnal AUC, mean glucose, and mean daytime glucose were higher in the obese subjects compared with normal-weight subjects in both early and late () pregnancy. Late in pregnancy, nearly all glycemic indices were statistically higher in the obese group compared with the normal-weight group (). Both 1- and 2-h mean postprandial glucoses were significantly higher in the obese women late in pregnancy (P < 0.001) on the controlled diet (115 ± 2 and 107 ± 2 mg/dL, respectively) compared with normal-weight women (102 ± 2 and 96 ± 2 mg/dL), and mean nocturnal glucose was higher in the obese women (96 ± 4 vs. 80 ± 2 mg/dL; P < 0.01). Although the 1- and 2-h postprandial glucose concentrations in the obese group late in pregnancy were ~10 mg/dL higher than in the normal-weight group, the highest mean 1-h postprandial value in the obese group was 116 ± 4 mg/dL after breakfast, and the highest mean 2-h postprandial value was 110 ± 5 mg/dL after dinner, compared with 104 ± 3 and 95 ± 3 mg/dL, respectively, in normal-weight women ().
Figure 1 Blood glucose measurements recorded by CGMS in lean and obese women early (A, C, and E) and late (B, D, and F) in pregnancy. Mean values ± SEM are listed by each data point for lean (○) and obese (●) women throughout the day and (more ...)
To portray all available data, CGMS data from normal-weight and obese subjects are depicted in as the percentage of relative cumulative frequency curves for both early () and late () pregnancy, using an approach described by Raichi et al. (12
). The curve for the obese mothers was shifted to the right, confirming that obese subjects exhibited more glucose values at higher levels compared with normal-weight subjects. In late pregnancy (), 95% of all of the glucose values in normal-weight subjects were ≤116 mg/dL compared with <133 mg/dL in obese women. In normal-weight subjects late in pregnancy, 80% of glucose values were <103 mg/dL compared with 117 mg/dL in the obese subjects. The 24-h glucose AUC was significantly higher in obese compared with normal-weight women in both early (P
< 0.05; ) and late (P
< 0.01; ) pregnancy. Finally, the time spent with glucose >120 mg/dL during 24 h was significantly longer in obese compared with normal-weight women (209 ± 62 vs. 33 ± 12 min, P
= 0.001) during late pregnancy.
depicts the statistically significant correlates between the metabolic measures and infant percentage body fat independent of maternal BMI. Infants born to obese mothers had significantly higher percentage body fat compared with those born to normal-weight mothers (9.2 ± 0.5 vs. 7.3 ± 0.4%, P < 0.01). Although birth weight was correlated with infant percentage body fat (r = 0.63, P < 0.001), none of the metabolic measures correlated with birth weight (data not shown). It was a surprise to find that maternal fasting triglycerides, measured only early in pregnancy, demonstrated the highest correlation with infant percentage body fat (r = 0.67, P < 0.001). Late in pregnancy, FFAs showed the highest correlation (r = 0.54, P < 0.01). Fasting insulin (r = 0.49, P < 0.05), mean daytime glucose (r = 0.48, P < 0.05), 24-h mean glucose (r = 0.44, P < 0.05), and 1-h postprandial dinner glucose (r = 0.44, P < 0.05) also were correlated with infant percentage body fat. Early maternal BMI was correlated with infant percentage body fat (r = 0.54, P < 0.001). However, in a stepwise regression analysis that included maternal BMI, early triglycerides, fasting FFAs late, fasting insulin late, and daytime mean glucose late, early triglycerides explained 40% of the variance in infant percentage body fat, and the other variables did not add statistically to the predictive power.
Figure 2 Relationships between maternal glucose, other plasma measurements, and infant adiposity. Triceps, subscapular skinfolds, and abdominal circumference were measured in triplicate by a single trained observer within 48 h of birth. The sum of the two skinfold (more ...)