Influence of pregnancy weight gain on the size of infants born to underweight women.

The influence of weight gain during pregnancy on duration of gestation and infant size at birth was examined among women beginning pregnancy underweight and at normal weight. Results of the review of 654 prenatal and delivery records revealed that 1) Prepregnancy weight status was not associated with the amount of weight gained during pregnancy; 2) underweight women who gained the same amount of weight as normal weight women delivered infants at a younger gestational age and of lower birth weight and length; 3) more than half the infants born to underweight women failing to gain more than 9 kg during pregnancy weighed less than 2501 g. These results suggest that recommendations for weight gain during pregnancy be based on prepregnancy weight status and that adequate weight gain is of critical importance to women beginning pregnancy underweight.