Weight gain during adolescent pregnancy. Associated maternal characteristics and effects on birth weight.

Prospective data from 696 adolescents who delivered at 37 weeks or more gestation were analyzed to determine factors associated with weight gain during pregnancy and effects of pregnancy gains on birth weight and other outcomes of pregnancy. Pregnancy weight gain was found to be associated with the following factors: mother's ethnicity, length of gestation, parity, and presence of pregnancy-related hypertension. Maternal weight gain during pregnancy markedly increased infant birth weight. The risk of a low birth-rate infant was greatly reduced (OR = 0.14; CL = 0.1-0.2), and the risk of a macrosomic infant was 13.1 times higher (OR = 13.1; CL = 8.9-19.2) in adolescents gaining 20 kg or more. There was no increased risk for Caesarean section, fetal/neonatal death, or neonatal intensive care unit admission based on maternal weight gain. No effect of prepregnant relative weight on maternal weight gain was detected. The effect of weight gain on birth weight was also independent of the maternal prepregnant relative weight.