Objective: Our purpose was to identify factors affecting fetal growth with birth weight and body composition.
Study design: A total of 183 singleton infants had birth weights and estimates of body composition performed within 24 hours of birth. Independent variables included were (1) maternal height, weight, pregravid weight, weight gain, education, and parity, (2) paternal height and weight, and (3) neonatal sex and gestational age. Best-fit stepwise regression analysis was used to correlate the independent variables with birth weight, fat-free mass, and fat mass.
Results: Compared with females, males had greater birth weight (p = 0.009) and fat-free mass (p = 0.0001) but not fat mass (p = 0.32). The strongest predictors were gestational age with birth weight (R2 = 0.10), neonatal sex with fat-free mass (R2 = 0.08), and parity with fat mass (R2 = 0.08). By use of the significant independent variables we explained 29% of the variation in birth weight, 30% in fat-free mass, and 17% in fat mass.
Conclusion: These data support the concept that various genetic and environmental factors may modify fetal growth by differentially affecting growth of fetal fat and fat-free mass.