Morbidity and mortality factors in twins. An epidemiologic approach.

Some epidemiologic characteristics of twin pregnancies and twin infants have been reviewed. We found that twins are prone to be born prematurely and have lower birth weights than their singleton counterparts after 30 to 34 weeks of gestation. Twins are also more prone to birth asphyxia, hyaline membrane disease, respiratory disorders, and seizures. Congenital anomalies and nonrespiratory morbidity were not found to be increased in twins. Twins have a six times higher perinatal mortality rate than do singletons. This is accounted for by prematurity in the main. A part of the excess mortality in twins is accounted for by a higher mortality in larger, near-term twins. Efforts should be directed toward decreasing the incidence of prematurity in twins and understanding and managing the problems of near-term twins better.