Late selective termination in dichorionic twins: comparing late second and third trimester procedures.

RESEARCH QUESTION:Do perinatal outcomes of selective termination performed in the late second versus third trimester differ and what risk factors are associated with subsequent preterm birth? DESIGN:This is a retrospective cohort study of late selective terminations performed in dichorionic twins between 2009 and 2021. Perinatal outcomes were compared between two groups: group A, late second trimester (20.2 to 24.2 weeks, n = 26), and group B, third trimester (≥28.2 weeks, n = 55) selective terminations. Univariate and multivariate analyses were conducted to identify factors associated with post-procedure preterm birth. RESULTS:In total, 81 dichorionic twin pregnancies were included. There were no pregnancy losses but 16% (13/81) of cases experienced complications. Group A had a higher median birthweight centile (36.5th versus 15th centile, P = 0.002) and lower rates of intrauterine growth restriction (IUGR) and Caesarean delivery (11.5% versus 32.7%, P = 0.04; and 26.9% versus 61.8%, P = 0.003) than group B. Preterm birth rates were similar (46.2% versus 63.6%, P = 0.15). Multiple regression revealed that reduction of the presenting twin and cervical length ≤35 mm were independently associated with post-procedure preterm birth (odds ratio [OR] 8.7, P = 0.001, 95% confidence interval [CI] 2.5-29.8; OR 3.8, P = 0.015, 95% CI 1.3-11). CONCLUSIONS:Late second trimester selective termination is associated with a higher birthweight centile and lower rates of IUGR and Caesarean delivery, compared with third trimester selective termination. Cervical length 35 mm or less and reduction of the presenting twin are independent risk factors for post-procedural preterm birth. These findings may help determine the optimal time to perform a late selective termination.