Influence of spontaneous fetal reduction on dichorionic diamniotic twin pregnancy outcomes after in vitro fertilization: a large-sample retrospective study

Objective: To examine the incidence of spontaneous fetal reduction during dichorionic diamniotic (DCDA) twin pregnancy after in vitro fertilization and embryo transfer (IVF-ET) and its influence on pregnancy outcomes.Methods: This was a retrospective cohort study of 4447 DCDA twin pregnancies and 14,551 singleton pregnancies after IVF-ET at a single center between 2009 and 2015. The spontaneous pregnancy reduction (SPR) group included 759 women. The remaining 3688 women with DCDA twins showing no spontaneous reduction were included in the non-SPR group. Outcomes were compared to a singleton group (n=14,551) treated over the same period. The overall rate of spontaneous reduction and frequency distribution across gestational epochs were determined and pregnancy outcomes were compared among the three groups. Further regression analysis was conducted to investigate whether spontaneous reduction was an independent risk factor for decreased take-home baby rate.Results: The overall rate of spontaneous DCDA twin reduction after IVF-ET was 17.1%, with most cases (89.8%) occurring in the first trimester. Pregnancy outcome measures, including miscarriage rate, premature delivery rate, live birth rate, take-home baby rate, gestational age of delivery, and neonatal birth weight, were significantly better in the SPR group than the non-SPR group. Live birth rate, take-home baby rate, neonatal birth weight, and other primary outcome measures in the SPR group were not inferior to the singleton group. Multivariate regression analysis showed that the take-home baby rate was significantly lower in the non-SPR group (OR =0.73, 95%CI: 0.44-0.92, p=.008) and that SPR did not decrease the take-home baby rate.Conclusions: Spontaneous pregnancy reduction is common in DCDA twin pregnancy after IVF-ET, but has little adverse influence on pregnancy outcomes and does not reduce the probability of taking home live babies.