Maternal weight gain during pregnancy and risks of small for gestational age and large for gestational age newborn

Objective: To define maternal body weight gain using body mass index in term uncomplicated live singleton deliveries with appropriate birth weight for low, normal, and high body mass index women. To also define the risks of small for gestational age and large for gestational age in each group. Methods: This is a study of 16,332 pregnant women who delivered at Chang Gung medical center from July 1990 to December 1995. Study subjects were women who delivered uncomplicated live term singletons without fetal anomaly. Subjects were divided into three groups by pre-pregnant body mass index as body mass index < 19.8 (low body mass index, n = 7277), 19.8 ≤ body mass index ≤ 24.2 (normal body mass index, n = 7920), and body mass index > 24.2 (high body mass index, n = 1135). The birth weight and the increment of body mass index from pre-pregnancy to term was analyzed among the three body mass index groups. Results: The increments of body mass index were 5.962 ± 1.411, 5.837 ± 1.539, and 5.292 ± 1.627 in low, normal, and high body mass index, respectively, for each group to deliver an appropriate birth weight baby. The difference among each group is extremely significant (P < 0.001). For the mean body height of each group (158.8 cm (62.5 in), 158.0 cm (62.2 in), and 157.7 cm (62.1 in)) the increments of body weight were 15.03 kg (33.14 lb), 14.57 kg (32.12 lb), and 13.16 kg (29.01 lb) to term. Adjustment of body weight increment by 0.97 kg (2.14 lb), 0.95 kg (2.09 lb), and 0.86 kg (1.90 lb) for a 5-cm (2.0 in) difference in each group is necessary. There was a high degree of positive correlation between the increase in body mass index during gestation and the percentage of small for gestational age or large for gestational age babies delivered. Conclusions: A significant difference was observed in maternal body weight gain during pregnancy between pre-pregnancy low, normal, and high body mass index women who delivered singletons with appropriate birth weight for gestational age. Specific nutritional counseling programs for different groups according to pre-pregnancy body mass index are mandatory.