Objective: To evaluate the efficacy of long-term indomethacin therapy (LIT) in prolonging pregnancy and reducing spontaneous preterm birth (PTB) in patients undergoing fetoscopic laser surgery (FLS) for the management of twin-to-twin transfusion syndrome (TTTS). Design: Retrospective cohort study of prospectively collected data. Setting: Collaborative multicenter study Population: 557 consecutive TTTS cases that underwent FLS Methods: LIT was defined as indomethacin use for at least 48 hours. Log-binomial regression was used to estimate the relative risk (RR) of PTB in LIT compared to non-LIT group. Cox regression was used to evaluate the association between LIT use and FLS-to-delivery survival. Main outcome measures: gestational age (GA) at delivery Results: Among the 411 pregnancies included, a total of 180 patients (43.8%) received LIT after FLS and 231 patients (56.2%) did not. Median GA at fetal intervention did not differ between groups (20.4 weeks). Median GA at delivery was significantly higher in the LIT group (33.6 weeks) compared to the non-LIT group (31.1weeks), p<0.001. FLS-to-delivery interval was significantly longer in the LIT group (P<0.001). The risk of PTB prior to 34, 32, 28, and 26 weeks gestation were all significantly lower in the LIT group compared to the non-LIT group (RR=0.69, 0.51, 0.37, and 0.18, respectively). The number needed to treat (NNT) with LIT to prevent one PTB<32 weeks gestation was 4, and to prevent one PTB<34 weeks was 5. Conclusion: Long-term indomethacin after FLS for TTTS was found to be associated with prolongation of pregnancy and reducing the risk for PTB.

Objective: To evaluate the role of intertwin differences in umbilical artery (UA) pulsatility index (DUAPI) in predicting infant survival in twin-to-twin transfusion syndrome (TTTS) Design: Retrospective cohort study Setting: Baylor College of Medicine, Texas Children’s Hospital and University of Maryland School of Medicine Population: Women who underwent laser surgery due to TTTS between 2002 and 2018. Methods: Absolute DUAPI were calculated prior to laser surgery. ROC analysis was done to derive a DUAPI cutoff value of 0.4 for the prediction of double infant survival. Regression analyses were performed to evaluate the association of DUAPI <0.4 and infant survival in the whole cohort, in TTTS cases with Quintero stages I/II and in those with Quintero stage III/IV; adjustments for gestational age at delivery, Quintero stage, selective fetal growth restriction (sFGR) and other confounders were done. Main Outcome Measure: Double infant survival to 30 days of life Results: 349 TTTS cases were included. Double twin survival to 30 days was observed in 67% (234/349) of cases. Intertwin DUAPI <0.4 was associated with increased double twin survival in the whole cohort (aOR: 3.40; 95% CI: 2.02-5.70; p<0.001), in women with TTTS Quintero stage I or II (aOR: 3.05; 95% CI: 1.32-7.09; p=0.009) and in women with TTTS Quintero stage III or IV (aOR: 3.23; 95% CI: 1.52-8.85; p=0.002). Neither Quintero stage nor sFGR were associated with infant survival. Conclusions: Intertwin differences in UA pulsatility index supersede the Quintero classification in the prediction of double infant survival following laser surgery in TTTS cases.