Congenital malformation in twins.

Abstract

Data from the population-based Metropolitan Atlanta Congenital Defects Program (MACDP) show that the overall rate of malformed infants, as well as the incidence of several specific defects, is higher for twins than for singletons. This elevated risk appears limited to same sex twins and, hence, is probably related to monozygosity. In addition to an 18-fold increase in risk of fetal death compared to singletons, twins have almost a 50% greater likelihood of congenital malformation.