Fetal and infant death in mono- and dizygotic twins in Englandand Wales 1982-91

摘要

AIM—To quantify the level of risk for stillbirth and infant death in singleton compared with twin pregnancies, using national data; to determine the independent effects of zygosity, sex, and birthweight on these risks in twin pregnancies.
METHODS—A retrospective national study was carried out of all singleton and twin birth and death registrations in England and Wales 1982-91, according to sex and birthweight group. Weinberg's rule was applied to the twin pairs to differentiate mono- from dizygotic twins. Relative risks for mono- compared with dizygous twins for both twins being stillbirths and for one of the pair being a stillbirth were determined. For twins where one was stillborn and the other live born, the relative risk of neonatal and infant mortality in the surviving co-twin was determined.
RESULTS—There were 6 563 834 registered singletons and 70772 registered twin pairs for the period under study. Monozygotic twins had a relative risk of: 18.91 (95% CI 12.48-28.64) for both twins being stillborn; 1.63 (95% CI 1.48-1.79) for one twin being a stillbirth; and 2.26 (95% CI1.45-3.52) for the live born co-twin dying as a neonate. When bothtwins were live born and among singletons, the odds ratio for neonatalmortality of being male was 1.41 (95% CI 1.37-1.45) and there was ahighly significant negative association with birthweight. Afteradjusting for birthweight group and sex, twins had a reduced neonatalmortality compared with singletons: odds ratio 0.91 (95% CI0.85-0.96).
CONCLUSIONS—Fetaldeath in one of monozygotic twins has serious implications for survivalof the co-twin. Monochorionicity is probably the essential feature ofthe increased risk to the co-twin. It is imperative that all fetaldeaths in multiple pregnancies are recorded and chorionicity determinedif parents are to be adequately counselled.