Discordant or abnormal nuchal translucency in patients with TTTS requiring laser

Monochorionic (MC) twins with discordant or abnormal nuchal translucency (NT) measurements are at increased risk for the development of Twin to Twin Transfusion Syndrome (TTTS). We sought to determine if first trimester NT abnormalities or discordances in MC twins also correlates with TTTS severity at presentation. Retrospective analysis of patients undergoing fetoscopic laser for TTTS with available first trimester NT measurements. Patients with first trimester NT discordance > 20% or crown rump length (CRL) adjusted NT > 95th percentile in at least one twin were compared to patients without discordance or abnormal NT measurements. We considered severe TTTS as advanced stage (III/IV) or early presentation (< 18 weeks). Groups were compared for maternal and fetal characteristics, and obstetric complications, and survival. Patients were offered genetic testing at the time of laser. 152 of 297 women (51.2%) were eligible for inclusion. Sixty-three (41.4%) had a history of discordant or abnormal first trimester NT. TTTS severity (p=0.40), performance of genetic testing (p=0.75), and genetic test abnormalities (p=1) were equally distributed between groups. Selective fetal growth restriction (sFGR) was more common in the group with discordant or abnormal NT (52.4% vs 32.6%, p=0.01), which remained significant after multivariate analysis controlling for CRL discordance (OR: 2.12, 95% CI: 1.09 – 4.15). There was a nonsignificant trend towards more anomalies in recipient twins in the discordant or abnormal NT group (22% vs 12% respectively, p=0.11). In this cohort of patients with TTTS, discordant or abnormal NT was not related to disease severity at presentation or genetic abnormalities. The potential association with second trimester growth disorder and recipient anomalies deserves further study.