A cord C-peptide result was available for 19,885 babies of the 23,316 blinded HAPO Study participants who were included in the first report of HAPO Study results (
2). Results shown in are from those 19,885 babies and their mothers. Mean maternal BMI at the OGTT was 27.5, and the correlation with prepregnant BMI, which was based on self-reported prepregnant weight, is 0.92. Mean glucose levels among this group were 4.5, 7.5, and 6.2 mmol/l for fasting, 1-h, and 2-h plasma glucose, respectively. Mean gestational age at delivery was 39.4 weeks, and the mean birth weight was 3,308 g. Skin fold measurements were available for 19,389 babies overall and for ~17,100 babies with a cord C-peptide result.
| TABLE 1Characteristics of HAPO participants* |
and show associations of maternal glucose with sum of skin folds >90th percentile and percent body fat >90th percentile, including ORs and 95% CIs for each category compared with the lowest or referent category. Overall, 1,863 (9.6%) babies had a sum of skin folds >90th percentile and 9.8% a percent body fat >90th percentile. With higher levels of maternal fasting, 1-, and 2-h plasma glucose concentrations, the proportion of babies with sum of skin folds or percent body fat >90th percentile rose, for example from 5.3 to 26.4% across FPG categories for sum of skin folds and from 6.2 to 27.7% for percent body fat. In model I, the OR was 6.42 in the highest category of FPG for sum of skin folds and 5.77 for percent body fat. For sum of skin folds, there was modest attenuation of the ORs with adjustment for model II confounders for all three glucose measures. For percent body fat >90th percentile, the ORs for FPG were modestly attenuated but became larger for 1- and 2-h plasma glucose. For both measures of neonatal adiposity, there was a strong graded association across increasing levels of maternal glycemia. In continuous variable models for sum of skin folds >90th percentile, ORs ranged from 1.37 to 1.52 in model I and 1.36 to 1.42 in model II for each measure higher by 1 SD. In addition, for percent body fat >90th percentile ORs ranged from 1.33 to 1.47 for model I and 1.35 to 1.44 for model II. There were no significant nonlinear associations for glucose or significant interactions with field center, BMI, height, or MAP. There was, however, a significant interaction for 1-h plasma glucose and age in relation to sum of skin folds >90th percentile, suggesting a stronger association of 1-h plasma glucose with this outcome with increasing maternal age.
| TABLE 2Relationship between maternal glucose and sum of skin folds >90th percentile* |
| TABLE 3Relationship between maternal glucose and percent body fat >90th percentile* |
Associations of glucose measures in continuous variable models for fat-free mass >90th percentile showed similar associations to those for percent fat >90th percentile, with ORs in model II ranging from 1.30 to 1.44 (data not shown). When birth weight, sum of skin folds, percent fat, and fat free mass were modeled as continuous variables in multiple regression analyses with adjustment for the same confounders (model II), mean differences between the highest and lowest categories for the glucose measures ranged from 242 to 305 g for birth weight, 1.4 to 2.0 mm for sum of skin folds, 1.5 to 2.5% for percent fat, and 157 to 168 g for fat free mass (all P < 0.001).
shows relationships between maternal glucose and individual skin folds >90th percentile in continuous variable analyses. Each individual skin fold measurement was positively related to maternal glycemia. Strongest associations were with subscapular skin fold where ORs for each glucose measure higher by 1 SD ranged from 1.40 to 1.56 in model I and from 1.37 to 1.47 in model II. For triceps skin fold, ORs ranged from 1.38 to 1.50 in model I and from 1.38 to 1.40 in model II; whereas for flank skin fold, ORs ranged from 1.29 to 1.44 in model I and from 1.28 to 1.35 in model II. Associations did not vary significantly by field center, BMI, height, or MAP for any of these outcomes. There was, however, a significant interaction of 1-h plasma glucose with age in the model II analysis for triceps skin fold, which suggested a stronger association of 1-h plasma glucose with triceps skin fold with increasing maternal age.
| TABLE 4Relationship* between maternal glucose and individual skin folds >90th percentile† |
When model II ORs for birth weight >90th percentile, percent body fat >90th percentile, or sum of skin folds >90th percentile associations with glucose as a continuous variable were adjusted for C-peptide (using linear and squared terms in C-peptide because of its nonlinear association with the outcomes) we found 23–38% reductions in the ORs for associations with individual glucose measures (data not shown).
Associations between categories of cord C-peptide and neonatal anthropometrics are shown in . With higher levels of cord C-peptide, frequency of each measure of size and adiposity rose. For example, the frequency of birth weight >90th percentile ranged from 4.5 to 25.6% across categories of cord C-peptide. In model I, ORs for the three measures ranged from 5.97 to 7.31 in the highest category of cord C-peptide. In model II, ORs were modestly attenuated, but strong graded associations remained.
| TABLE 5Relationship between cord serum C-peptide and neonatal anthropometrics |
When these outcomes and fat free mass were modeled as continuous variables in multiple regression analyses with adjustment for the same confounders (model II), mean differences between the highest and lowest categories for cord C-peptide were 345 g for birth weight, 2.0 mm for sum of skin folds, 2.7% for percent fat, and 221 g for fat free mass (all P < 0.001) (data not shown).
shows associations between cord C-peptide and individual skin folds >90th percentile. Results for both model I and model II show that subscapular skin fold has the strongest and flank skin fold the weakest association with cord C-peptide level, with ORs for the highest versus lowest category of 6.79 and 5.54 in models I and II, respectively, for subscapular skin fold and 3.78 and 3.17 for flank skin fold.
| TABLE 6Relationship between cord serum C-peptide and individual skin folds |