Late selective termination: comparing outcomes of late second and third trimester procedures

Research Question To compare perinatal outcome of selective termination (ST) performed in the late 2nd versus 3rd trimester and to identify risk factors associated with subsequent preterm birth. Design Retrospective cohort study of late selective terminations (≥20 weeks of gestation) performed in dichorionic twins, between 2009-2021. Perinatal outcomes were compared between 2 groups: A) Late 2nd trimester (200/7-240/7 weeks, N=26) and B) 3rd trimester (≥ 280/7 weeks, N=55) STs. Univariate and multivariate analyses were conducted to identify factors associated with post-procedure preterm birth. Results A total of 81 dichorionic twin pregnancies were included in the study. There were no pregnancy losses but 16% (13/81) of cases experienced complications. Group A had a higher median birthweight centile (51.5th versus 28th centile, P = 0.002), lower rates of IUGR and cesarean delivery (11.5% versus 32.7%, P = 0.04 and 26.9% versus 61.8%, P = 0.003, respectively) compared to group B. There was a similar rate of preterm birth (46.2% versus 63.6%, P = 0.15).Multiple regression revealed that reduction of the presenting twin and cervical length < 35 mm were both independently associated with post-procedure preterm birth (OR 8.7, P = 0.001, 95% CI 2.5-29.8 and OR 3.8, P = 0.015, 95% CI 1.3-11, respectively). Conclusion Late 2nd trimester ST is associated with a higher birthweight centile and lower rates of IUGR and cesarean delivery, compared to 3rd trimester ST. Cervical length < 35 mm and reduction of the presenting twin are independent risk factors of post-procedure preterm birth. These findings may aid to determine the optimal time to perform a late ST.