The aim of this study was to determine optimal maternal weight gain in
a singleton pregnancy and evaluate the current recommendations. We us
ed a historical prospective design to evaluate the association between
pregnancy weight gain and perinatal outcome. All singleton pregnancie
s without congenital anomalies delivered between 1987 and 1993 at a si
ngle institution in New York City were analyzed, After adjusting for t
he prepregnancy body mass index, we determined the weight gain associa
ted with optimal perinatal outcome. During this 6-year study period, 2
0,971 pregnant women met the inclusion criteria. Among them, 1,975 (9.
4%) had adverse perinatal outcome. Prepregnancy weight and weight gain
during pregnancy were strongly associated with adverse outcome. For w
omen of average size, optimal outcome was found in those who gained be
tween 31 and 40 pounds. For women underweight prior to pregnancy, opti
mal outcome occurred in those who gained 36-40 pounds. For women who w
ere overweight or obese, a gain of 26-30 pounds was associated with op
timal outcome. Weight gain during pregnancy is strongly associated wit
h perinatal outcome, independent of important confounding factors, and
should be carefully monitored during pregnancy. A randomized controll
ed trial is required to determine if perinatal and maternal outcome ca
n be improved by advising pregnant women to gain weight using these ne
w ranges :rather than the Institute of Medicine's recommendations.