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

摘要

AIM—To quantifythe level of risk for stillbirth and infant death in singletoncompared with twin pregnancies, using national data; to determine theindependent effects of zygosity, sex, and birthweight on theserisks in twin pregnancies.
METHODS—Aretrospective national study was carried out of all singleton and twinbirth and death registrations in England and Wales 1982-91, accordingto sex and birthweight group. Weinberg's rule was applied to the twinpairs to differentiate mono- from dizygotic twins. Relative risks formono- compared with dizygous twins for both twins being stillbirths andfor one of the pair being a stillbirth were determined. For twins whereone was stillborn and the other live born, the relative risk ofneonatal and infant mortality in the surviving co-twin was determined.
RESULTS—Therewere 6 563 834 registered singletons and 70772 registered twin pairsfor 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.