Determinants of body fat in infants of women with gestational diabetes mellitus differ with fetal sex

OBJECTIVE

Neonatal adiposity is a well-recognized complication of gestational diabetes mellitus (GDM). This study aimed to identify factors influencing adiposity in male and female infants of women treated for GDM.

RESEARCH DESIGN AND METHODS

This was a prospective study of 84 women with GDM. Daily blood glucose levels (BGLs) were retrieved from glucose meters, and overall mean fasting and mean 2-h postprandial BGLs were calculated for each woman. Infant body composition was measured at birth, and regression analysis was used to identify significant predictors of infant body fat separately in male and female infants.

RESULTS

Maternal fasting BGL was the major predictor of adiposity in male infants but had little relationship to adiposity in female infants. In male infants, percent fat was increased by 0.44% for each 0.1 mmol/L increase in mean maternal fasting BGL. Maternal BMI was the primary predictor in female infants but had little effect in males. In female infants, percent fat was increased by 0.11% for each 1 kg/m² increase in maternal prepregnancy BMI.

CONCLUSIONS

Fetal sex may influence the impact that treatment strategies for GDM have on infant adiposity.The maternal metabolic disturbance of gestational diabetes mellitus (GDM) affects fetal development and alters birth weight, BMI, and percent body fat at birth (1,2). Current treatment of GDM achieves normalization of birth weight and reduces neonatal complications (3). However, the effects of GDM on the offspring extend well beyond the fetal period and, thus, offspring of women with GDM also have an increased risk of unfavorable long-term outcomes such as obesity and diabetes, well above that explained by genetics alone (4), even after treatment.To date, studies designed to inform optimal treatment of GDM have focused on normalization of birth weight, but neonatal adiposity may be a more sensitive marker of disturbed in utero metabolism, risk of obesity, and poor long-term health than birth weight alone (1). Body fat at birth is elevated in infants born to women with GDM even when birth weight is normal (1). In a group of 6- to 12-year-old children born to women with GDM, percent body fat in childhood was significantly correlated to body fat at birth, but there was no relationship between birth weight and weight at the time of study (5). Even though treatment of mild GDM does reduce the incidence of macrosomia, it does not reduce the incidence of obesity in the offspring at 4–5 years (6).To interrupt the obesity cycle and reduce the risk of future poor adult health, it may be necessary to normalize neonatal adiposity as well as birth weight. To do this, it is essential to understand the factors that determine adiposity in infants of women with GDM.While genetic factors may be the primary determinant of lean body mass, fetal fat mass may be more strongly influenced by the in utero environment (7). A range of maternal factors have been identified as determinants of neonatal size and body fat, including maternal BMI, parity, maternal glucose concentration, and insulin sensitivity (8–10). Higher gestational weight gain is associated with increased infant birth weight in lean and moderately overweight women (11) and in women with normal glucose tolerance (9) but not in obese women (11) or women with GDM (9). However, the factors influencing fetal fat accretion remain poorly understood.Both body weight and body composition at birth are different in male and female infants (12), and sex of the infant has been reported as a significant determinant of each (9). We hypothesized that the determinants of fetal body composition may also differ with fetal sex. The aim of this study was to identify factors that influence adiposity in male and female infants born to women treated for GDM.