Evaluating the safety and outcomes of third-trimester selective termination in dichorionic twin pregnancies with discordant anomalies—a standardized approach for counseling

OBJECTIVE: To evaluate procedure-related preterm birth (PTB) following third-trimester selective termination (ST) in DC twins and to compare delivery timing with expectantly managed discordant DC twins and non-anomalous DC twins. METHODS: A retrospective cohort study was conducted of all DC twin pregnancies undergoing third-trimester ST (> 28 weeks) at a tertiary care center (2003-2023). Pregnancies were classified as having procedure-related complications (delivery ≤ 4 weeks) or uneventful (delivery > 4 weeks). Comparator cohorts included expectantly managed discordant DC twins and non-anomalous DC twins. Outcomes included timing of delivery, cumulative incidence of PTB, and risk factor analysis. RESULTS: 90 women with DC twin pregnancies elected for ST and 85 procedures were completed. Outcome was available for 81 cases; 48 (59.3%) delivered ≤ 4 weeks after ST and 33 (40.7%) delivered later. Clinical chorioamnionitis was more common within the group delivered ≤ 4 weeks (35.4% vs. 0%; p = 0.001). Cumulative PTB incidence showed accelerated delivery between 32 and 34 weeks after ST. Independent risk factors for delivery ≤ 4 weeks included polyhydramnios (OR 5.68) and reduction of the presenting fetus (OR 6.51). Comparator cohorts exhibited substantially lower PTB incidence. CONCLUSION: Third-trimester ST in DC twins is associated with high PTB risk, but excellent co-twin survival. The first 4 weeks after ST represent a critical vulnerability period, and risk is strongly influenced by identifiable preprocedural factors. These findings support individualized counseling, later scheduling in high-risk pregnancies, should be considered.