Late Selective Termination and the Occurrence of Placental-Related Pregnancy Complications: A Case Control Study.

Introduction: Multiple pregnancies are at increased risk of placental-related complications. The aim of the study was to investigate the prevalence and cumulative incidence of placental-related complications in twin pregnancies undergoing a late selective termination, compared to matched singleton and twin controls. Methods: A retrospective case-control study of post-selective late termination (>= 20 weeks of gestation) singletons performed between 2009 and 2020 at a single tertiary center. Each post-termination pregnancy was matched to 2 singleton and 2 dichorionic twin pregnancies for: mode of conception, maternal age group and parity. The prevalence of composite placental related outcome was determined and compared. Kaplan-Meier curves were constructed, and log rank test was performed to compare the cumulative incidence of placental complications among groups. Results: Included were 90 post-selective termination pregnancies and 360 matched singletons and twins. These were subdivided according to trimester at procedure: 1) late 2nd trimester (N = 43, 20-27.6 weeks); 2) 3rd trimester (N = 47, >= 28 weeks). Placental-related complications presented earlier in the 3rd trimester selective termination group compared to singletons (median 35.5 vs median 37.4 weeks of gestation, P = 0.01). The cumulative incidence of placental-related complications in twins and post-selective termination singletons rose significantly earlier compared to singletons (P < 0.0001). A late 2nd trimester selective termination resulted in a comparable gestational age and cumulative incidence of placental-related complications as singletons. Discussion: Compared to singletons, the cumulative incidence of placental complications rises significantly earlier in post-third trimester selective termination singleton pregnancies. While a late 2nd trimester selective termination results in a cumulative incidence comparable to singletons.