AIM: This study investigated whether newborn body composition is influenced by prepregnancy obesity and gestational weight gain (GWG) and explored any associations between body composition and birthweight standard score (z-score), categorised by size for gestational age.

METHODS: We recruited 231 obese and 80 normal weight mothers and their newborn infants and assessed the babies' body composition using dual-energy X-ray absorptiometry.

RESULTS: The total and abdominal fat masses of infants born to mother who were obese before pregnancy were 135 g (p < 0.001) and 18 g (p < 0.001) higher than the offspring of normal weight mothers. The infants' fat mass increased by 11 g (p < 0.001) for every kilogram of GWG. There were no associations between prepregnancy obesity and fat-free mass. The fat percentage was significantly higher in infants who were large for gestational age (15.3%) than small for gestational age (5.2%) and appropriate for gestational age (9.8%) (p < 0.001). Lower birthweight z-score was associated with a higher proportion of abdominal fat mass (p = 0.009).

CONCLUSION: Infants born to obese mothers had higher fat mass at birth, with abdominal fat accumulation. Low birthweight was associated with a lower crude abdominal fat mass, but a higher proportion of total fat mass placed abdominally.