With the aid of the national Medical Birth Registries and Discharge Registries in Denmark and Sweden it was possible to identify and study delivery outcome in 77 women who, prior to pregnancy, had undergone an intestinal bypass operation for obesity. Analysis of birth weight and pregnancy length distribution showed that infants borne by these women had an increased rate of low birth weight, short gestation, and also growth retardation. There were no distinct differences between those infants that were conceived less than 24 months or more than 24 months after operation. Only two infants had congenital malformations, none died perinatally.