Clinical outcomes in higher-order multiples reduced to dichorionic diamniotic (DCDA) twins compared with primary twins and singletons: A prospective observational study.

Objective: To compare outcomes in higher-order multiple pregnancies reduced to dichorionic diamniotic (DCDA) twins with primary DCDA twins and singleton pregnancies.

Methods: This prospective observational study included all higher-order multiple pregnancies that underwent ultrasound-guided transabdominal fetal reduction at 11-13 weeks of gestation from January 2018 to June 2020. Outcomes were compared with 100 primary DCDA twins and 1078 singletons.

Results: Sixty-four higher-order multiples underwent reduction at mean gestational age of 11.46 weeks. Of the reduced pregnancies, 3.12% resulted in miscarriage before 24 weeks compared with 2% (2/100) of primary twins and 0.74% of singletons (P = 0.09). The mean gestational age at delivery was 33.48 weeks for reduced twins, 34.52 weeks for primary twins (P = 0.10) and 38.14 weeks for singletons (P < 0.001). Compared with primary twins, the adjusted odds of preterm delivery before 34 weeks and before 36 weeks for reduced twins were 0.56 (95% confidence interval [CI] 0.48-3.54, P = 0.62) and 0.84 (95% CI 0.78-8.85, P = 0.08), respectively. There was no significant difference in rates of pre-eclampsia, Cesarean delivery, birth weight below the 10th and 3rd centiles, and perinatal mortality among primary and reduced twins. All risks were significantly lower in singleton pregnancies.

Conclusion: Reduced twins have similar obstetric and perinatal outcomes as primary twins, but adverse outcomes are significantly higher in both groups when compared with singleton pregnancies.