279: Midtrimester isolated oligohydramnios in monochorionic diamniotic multiple gestations

Abstract

To describe outcomes in monochorionic diamniotic multiple gestations with midtrimester isolated oligohydramnios (iOligo). This is a retrospective study of iOligo patients initially referred for treatment of evolving twin-twin transfusion syndrome (TTTS) or selective intrauterine growth restriction (sIUGR) Type II (persistent absent or reversed umbilical artery end diastolic flow). iOligo was defined as a maximum vertical pocket of amniotic fluid of ≤ 2 cm in the iOligo twin’s sac and > 2 and < 8 cm in the co-twin’s sac. Patients who did not develop subsequent TTTS or sIUGR Type II were classified as Group I, and patients that did develop TTTS or sIUGR Type II were classified as Group II. Of 868 referred patients, 41 (4.7%) were initially diagnosed with iOligo. After initial consultation, 2 patients terminated and 1 was lost to follow-up, leaving 38 iOligo patients. Twelve (31.6%) were classified as Group I, and 26 (68.4%) were classified as Group II. In Group I, 11 of 12 were expectantly managed, which resulted in fetal demise of the iOligo twin in 2/11 (18.2%) with a median gestational age (GA) at delivery of 34.7 weeks (range 18.0 - 36.4), a 30-day perinatal survival of at-least-one twin of 90.9% (10/11), and dual 30-day survivors in 9/11 (81.8%). One of the 12 had an umbilical cord occlusion for sIUGR complicated by intermittent absent umbilical artery end-diastolic flow, fetal anomalies, and recurrent fetal heart rate decelerations. In Group II (N=26), 15 (57.7%) developed TTTS and 11 (42.3%) developed sIUGR Type II. Laser surgery was performed for 18 of the Group II patients, who subsequently reached a median GA at delivery of 33.9 weeks (range 26.4 - 37.1); fetal demise of the iOligo twin occurred in 9/18 (50.0%), and 30-day perinatal survival of at-least-one twin was 100% (18/18) and dual survivorship was 44.4% (8/18). The majority (68%) of monochorionic diamniotic multiple gestations that presented in the second trimester with iOligo subsequently progressed to TTTS or sIUGR Type II.