A retrospective cohort study was undertaken to assess the relationship between maternal body mass index (BMI) and neonatal birth weight. Data were extracted from Aberdeen Maternity and Neonatal Databank on all deliveries (n = 94049) occurring between 1967 and 2010. Compared with mothers whose weight was in the normal range, the adjusted odds of delivering a high-birth-weight infant were 0.63 (95% confidence interval: 0.59, 0.67), 1.44 (1.39, 1.50); 1.83 (1.72, 1.95); 2.22 (2.04, 2.43) in underweight, overweight, obese and morbidly obese mothers, respectively. Similarly, the adjusted odds of delivering a low-birth-weight baby decreased with increasing maternal BMI from 1.38 (1.23, 1.55) in underweight women to 0.80 (0.72, 0.89) in overweight women; 0.78 (0.67, 0.93) in obese and 0.56 (0.44, 0.71) in morbidly obese mothers. These relationships were only evident after adjustment for gestational age, presumably because higher maternal BMI is also, in some cases, associated with pre-term deliveries.
- Birth weight
- maternal body mass index