Pregnancy outcomes associated with chorioamnion membrane separation severity following fetoscopic laser surgery for twin-twin transfusion syndrome

Objective: We tested the hypothesis that increasing severity of chorioamnion membrane separation (CAS) after fetoscopic laser surgery (FLS) for twin-twin transfusion syndrome (TTTS) is associated with worse pregnancy outcomes. Methods: Prospective cohort of patients undergoing FLS for TTTS between 2011 and 2018. CAS was defined as separation of fetal membranes from the uterine wall on post-operative ultrasound. Patient groups were defined: Group 1: No CAS; Group 2: CAS lower than 50th centile; Group 3: CAS upper than 50th centile or complete CAS. Comparative analysis was performed. Results: Of 387 patients meeting inclusion criteria, 29 (7.5%) had CAS (median 9.8 mm [4.9-30.8 mm]). Group 1 patients were more likely to undergo FLS at later gestational age, had increased recipient maximum vertical pocket, and higher amnioreduction volume than Group 3. Group 3 had higher rates of preterm premature rupture of membrane, delivered earlier and were more likely to terminate than Group 1. Group 2 had fewer neonatal survivors than Group 1. Survival analysis for gestational age at delivery and Cox proportional hazards model indicated increased risk for early delivery in Groups 2 and 3 compared with Group 1. Conclusions: Patients with CAS ≥9.8 mm or complete CAS after FLS for TTTS had worse obstetric and neonatal outcomes.