Perinatal and infant mortality in twins.

The perinatal and infant mortality in the sample of all children born in the South Moravian Region of Czechoslovakia in the years 1970--1976 was studied. The total number of births was 237,655, including 4,072 twin children. The perinatal mortality of twins was 11 times higher and the infant mortality of twins was six times higher than those of the singletons. The mortality of B twins was significantly higher, especially in the groups with birthweight of 1,000 to 2,499 gm and with a gestational age of 22--36 weeks. The most important causes of deaths in twins are prematurity and anoxia or hypoxia. The B twin is more at risk, but also for the A twin the risk is higher for the average singleton. This difference disappears when only the infants with low birthweights are compared.