684 Intertwin differences in umbilical artery pulsatility index and risk for twin-to-twin transfusion syndrome

Abstract

This study evaluates the role of intertwin differences in umbilical artery pulsatility index (DUAPI) in the identification of monochorionic diamniotic (MCDA) twin pregnancies at increased risk for twin-to-twin transfusion syndrome (TTTS) MCDA twin pregnancies evaluated at two institutions between 2002 and 2017 were included. Absolute intertwin DUAPI was calculated in the second trimester or prior to laser surgery. ROC curve analysis was performed to derive an intertwin DUAPI cutoff value of ≥0.1. Regression analyses were performed to evaluate the association of intertwin DUAPI ≥0.1 with TTTS, adjusted for selective fetal growth restriction and using DUAPI <0.1 as reference. Regression analysis restricted to Quintero stage I TTTS cases was also performed to determine the association of intertwin DUAPI ≥0.1 and laser surgery. 379 MCDA twin pregnancies were included with (n=287) and without (n=92) TTTS. A higher proportion of MCDA twin pregnancies with intertwin DUAPI ≥0.1 had TTTS compared to those with a intertwin DUAPI <0.1 [80.2% (231/288) vs. 61.5% (56/91); p<0.001]. Among Quintero stage I TTTS cases (n=61), a higher proportion of those with a DUAPI ≥0.1 had laser surgery compared to those with a DUAPI <0.1 [89.6% (43/48) vs. 53.8% (7/13); p=0.008]. The sensitivity, specificity, positive and negative predictive values, as well as positive likelihood ratios of a intertwin DUAPI ≥0.1 in the identification of TTTS were: 82%, 40.2%, 78.8%, 45%, and 1.37, respectively. When the analysis was restricted to Quintero stage I TTTS cases, the corresponding values in the prediction of laser surgery were: 86%, 54.6%, 89.6%, 46.1%, and 1.89. DUAPI ≥0.1 was associated with an adjusted Odds Ratio (aOR) of 2.65 (95% CI: 1.58-4.47) to have TTTS. Among Quintero stage I TTTS cases, an intertwin DUAPI ≥0.1 was associated with an aOR of 10.6 (95% CI: 1.13-52.58) to require laser surgery. Estimation of intertwin differences in umbilical artery impedance to blood flow may provide a novel approach to identify MCDA twin pregnancies at increased risk for TTTS and laser surgery