The relationship between weight gain in pregnancy, birth-weight and postpartum weight retention.

A total of 292 middle class, nonsmoking Chinese patients with known prepregnant weight who subsequently had uncomplicated singleton pregnancies delivering after 36 weeks' gestation were recruited to assess their serial antenatal weight gain, weight at 6 weeks and 3 months postpartum. The average prepregnant body mass index in the whole group was 20.4 kg/m2 (SD 2.19), and the total pregnancy weight gain was 14 kg (SD 3.75). Those with weight gain over 17.83 kg (one SD above the mean) (n=58) had higher weight gain in all 3 trimesters taken separately, as well as higher weight retention at 6 weeks and 3 months postpartum (p <0.001). Similar differences were noted for those with total weight gain over 2 standard deviations above the mean. The average weight retained at 3 months postpartum was 3.64 kg (SD 2.75). Those with weight retention over 9.14 kg (2 SD above the mean) (n=8) had a significantly higher second and third trimester weight gain (p <0.01) compared to the rest. These data suggest that excessive weight gain during pregnancy for women with prepregnant BMI in the normal range occurred most significantly after the mid-trimester, and was associated with higher postpartum weight retention without significant increase in birth-weight.