Infant mortality in twin pregnancies following in-utero demise of the co-twin

ObjectiveTo assess whether conversion from twin to singleton pregnancy following the demise of a co-twin influences survival.MethodsThis retrospective study compared the risk for neonatal, post-neonatal and infant death for converted co-twins versus unconverted co-twins using the US matched multiple file dataset for the period 1995–2000. We also examined the same risks for converted versus same-quantile co-twins, hazard ratios (HR) and 95% confidence intervals (CI) were computed using Cox Proportional Hazards models.ResultsThe risk for neonatal (HR = 0.18, 95% CI: 0.09–0.34 and HR = 0.69, 95% CI: 0.50–0.96) and infant death (HR = 0.22, 95% CI: 0.12–0.42 and HR = 0.57, 95% CI: 0.42–0.77) were significantly lower for converted twins than for unconverted twins and same-quantile twins, respectively. For black compared to white, the risk for post-neonatal death increased by 89% (HR = 1.89, 95% CI = 1.03, 3.48), and 79% (HR = 1.79, 95% CI = 1.53, 2.09) for converted vs. unconverted and converted vs. same-quantile, respectively. For converted black, the risk for neonatal death decreased by 17% (HR = 0.83, 95% CI = 0.73–0.93) as compared to unconverted.ConclusionsRisks for all mortality types were lower among converted co-twins than their unconverted or same-quantile counterparts. The lower neonatal and higher post-neonatal mortality among black require future research.