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Objective To examine trends in cause- and birthweight-specific fetal and neonatal mortality rates in twins and singletons.

Design Descriptive analysis based on a regional register.

Setting The Northern Health Region of England, 1982–1994.

Sample Two hundred and thirty-six fetal and 356 neonatal twin deaths; 2687 fetal and 2301 neonatal singleton deaths from a population of 10,734 twins and 505,477 singletons.

Main outcome measures Fetal and neonatal autopsy rates, cause- and birthweight-specific fetal and neonatal mortality rates in twins and singletons.

Results The extended perinatal mortality (including stillbirths and neonatal deaths) rate (EPMR) was 55.2 per 1000 in 1982–1994 in twins compared with 9.9 per 1000 in singletons. The relative risk for twin compared with singleton deaths was 5.6 (95% CI 5.1-6.1) being highest for immaturity (12.9, 95% CI 11.1–15.0). A significant decrease in the EPMR occurred in both twins and singletons in 1988–1994 compared with 1982–1987. The EPMR decreased mainly due to a reduction of deaths from antepartum asphyxia in twins and intrapartum asphyxia and trauma in singletons, as well as a reduction in congenital malformations in both groups. In both twins and singletons, birthweight-specific mortality rates improved between 1982–1987 and 1988–1994.

Conclusion The higher relative risk for twin deaths remained stable due to a similar decrease in the EPMR for both twins and singletons. The cause-specific relative risk in twins declined for antepartum asphyxia. The mortality rate resulting from lethal congenital malformations decreased in twins and singletons mainly due to earlier detection and subsequent termination of pregnancy.