Main Findings:
The results of our study demonstrate that intertwin differences in umbilical artery impedance to blood prior to laser surgery supersede the Quintero classification (or any of its sonographic criteria) in the prediction of double infant survival in TTTS cases. These observations are consistent with an earlier report indicating that intertwin DUAPI <0.4 is associated with increased infant survival in TTTS cases where both fetuses have positive end-diastolic flow in the umbilical arteries (Quintero stages I and II) prior to laser surgery9. This study further demonstrates that the same applies to TTTS cases with Quintero stages III or IV when the statistical analysis is adjusted for gestational age at delivery, sFGR, and other important confounders.