Impact of maternal body mass index on neonate birthweight and body composition

Objective

The purpose of this study was to compare bodyweight and composition (percent fat, fat mass, and fat-free mass) in neonates born to mothers with a normal pregravid body mass index (BMI; < 25 kg/m²) vs neonates born to mothers with an overweight/obese pregravid BMI (≥ 25 kg/m²).

Study Design

Seventy-two neonates (33 from normal mothers and 39 from overweight/obese mothers) of singleton pregnancies with normal glucose tolerance had their bodyweight and body composition assessed by air-displacement plethysmography.

Results

After controlling for neonate age at time of testing, significant differences were found between groups for percent fat (12.5 ± 4.2% vs 13.6 ± 4.3%; P ≤ .0001), fat mass (414.1 ± 264.2 vs 448.3 ± 262.2 g; P ≤ .05), and fat-free mass (3310.5 ± 344.6 vs 3162.2 ± 343.4 g; P ≤ .05), with no significant differences between birth length (50.7 ± 2.6 vs 49.6 ± 2.6 cm; P = .08) or birthweight (3433.0 ± 396.3 vs 3368.0 ± 399.6 g; P = .44).

Conclusion

Neonates born to mothers who have a normal BMI have significantly less total and relative fat and more fat-free mass than neonates born to overweight/obese mothers. Although preliminary, these data suggest that the antecedents of future disease risk (eg, cardiovascular disease, diabetes, and obesity) occur early in life.

Key words: body mass index, fetal programming, infant body fat, obesity, pregnancy