The impact of route of delivery and presentation on twin neonatal and infant mortality: a population-based study in the USA, 1995–97

Abstract

Objective: We examined whether the route of delivery for near-term ( ⩾ 34 weeks' gestation) twins, as candidates for vaginal delivery, affected neonatal and infant mortality rates. We further evaluated whether these mortality rates were modified by fetal presentation.Methods: A population-based retrospective cohort study based on the matched multiple births data in the USA (1995–97) was performed. Analyses were restricted to non-malformed liveborn twins delivered at ⩾ 34 weeks' gestation. Twins with breech–breech and breech–vertex presentations were excluded, since they are not candidates for vaginal delivery. Neonatal mortality rates (death within the first 27 days) and post-neonatal mortality rates (death between 28 and 365 days) per 1000 twin live births, by route of delivery and fetal presentation, were derived. The associations between neonatal mortality, post-neonatal mortality and the route of delivery for vertex–breech versus vertex–vertex presentations were expressed based on relative risks (RR) and 95% confidence intervals (CI) derived from logistic regression models based on the method of generalized estimating equations.Results: Of the 177 622 twins analyzed, 87% (n = 154 531) presented as vertex-vertex. Fifty-five per cent (n = 97 692) of twins were both delivered vaginally, 41% (n = 72 825) were both delivered by Cesarean section and, of the remaining 4% (n = 7105), the first twin was delivered vaginally and the second by Cesarean section. Twins with vertex–breech presentations delivered by Cesarean–cesarean sections, as well as those with vertex–vertex presentations delivered vaginally, had the lowest neonatal mortality rate (1.6 per 1000 live births). The highest neonatal mortality rate in the vertex–breech pairs occurred with vaginal–Cesarean deliveries (2.7 per 1000 live births). Among twins with vertex–vertex presentations, twins delivered via the vaginal–Cesarean route experienced the highest neonatal mortality (3.8 per 1000 live births). The RR for neonatal mortality in this group was 2.24 (95% CI 1.35, 3.72) compared with twins both delivered vaginally.Conclusion: Route of delivery and fetal presentation both confer an impact on twin infant mortality rates. Strategies to reduce discordant routes in complicated vaginal deliveries may lead to improved neonatal survival.