1150 Risk Factors for Preterm Delivery in Monochorionic Diamniotic Pregnancies Undergoing Selective Cord Occlusion

To review risk factors for preterm delivery in a cohort of monochorionic diamniotic twin pregnancies undergoing selective cord occlusion (SCO) using radiofrequency ablation (RFA). Single center retrospective analysis of complex monochorionic pregnancies managed with SCO via RFA between 2014-2022. The spontaneous preterm group was compared to the full-term delivery group. Correlation analysis between gestational age at SCO and gestational age at delivery was performed. Kaplan-Meier survival analysis was created for time to delivery between different diagnostic indications and log-rank test was performed. Total live birth rate in the twin population undergoing RFA was 86% (160/186) with a median gestational age at delivery of 36.1 weeks. Total survivor to discharge rate was 82.3% (153/186). To evaluate risk factors for premature birth, pregnancies with dual demise within the first post-operative week and iatrogenic preterm deliveries were excluded. A total of 155 pregnancies were evaluated - 76 (49%) had spontaneous preterm delivery and 79 (51%) delivered full term. Preoperative variables were comparable in the two groups. A higher proportion of women undergoing RFA for TTTS had spontaneous preterm delivery (34.2% versus 19%, p< 0.05). Adding amnioreduction in conjunction with RFA did not increase the risk of preterm delivery (13.2% vs 10.1%). The rest of the operative variables did not influence the rates of premature delivery. Gestational age at procedure did not correlate with gestational age at delivery (p=0.78). Kaplan–Meier curves showed that the proportion of pregnancies remaining undelivered from the time of radiofrequency ablation until 37 weeks’ gestation was lower for the indication of TTTS. Most perioperative variables did not influence the rates of spontaneous premature delivery in the monochorionic twin population undergoing RFA. Preoperative indication of TTTS was associated with an increased risk of preterm birth, possibly suggesting the underlying diagnosis increasing risk for prematurity rather than the procedure.