132: The earlier the better or the later the better: Optimal timing of fetal reduction from twins to singleton

Abstract

The aim of this study was to determine the rate of pregnancy complications, obstetrical and neonatal outcomes of twin pregnancies that underwent reduction to singleton at late first trimester versus second trimester. From January 2005 through September 2016, 221 dichorionic diamniotic twin pregnancies underwent reduction to singleton. Cases of selective reduction performed at 15-23 weeks of gestation due to fetal anomalies (group A, n=72), were compared to cases of fetal reduction performed at 11-14 weeks, mainly at patient’s request (group B, n=149). Group A underwent NT screening at 11-12 weeks and detailed anomaly scans beyond 14 weeks of gestation. Group B underwent NT screening at 11-12 weeks and detailed anomaly scans at 13+ weeks. Main outcome measures were rates of pregnancy complications, late abortions, preterm delivery and neonatal outcomes. Non-parametric statistical methods were employed. The rate of preterm delivery was significantly higher in late reduction than in early reduction at ≤37 weeks (33.3% in group A vs. 16.8% in group B, p=0.005), ≤34 weeks (13.9% vs. 2.7%, p=0.002) and at ≤32 weeks (9.7% vs. 2.7%, p=0.04). The upper fetus was reduced in 86.6% of the cases in group B, and in 76.4% of the cases in group A. In sub-analysis including only cases in which the upper twin was reduced, late reduction remained associated with higher rate of preterm birth prior to 37, 34 and 32 weeks of gestation compared with earlier reduction. There was no significant difference in the rate of pregnancy loss before 24 weeks’ gestation (0% in group A vs. 0.7% in group B), gestational diabetes, hypertensive diseases of pregnancy, preterm premature rupture of membranes and intrauterine growth restriction. Overall, the neonatal outcome was comparable between the groups, except for higher rates of respiratory distress syndrome (7.5% vs. 0.7%, p=0.01) and exposure to mechanical ventilation (9% vs. 1.4%, p=0.01) in group A. Second trimester reduction of twins is associated with an increased rate of prematurity compared to late first trimester reduction. However, the overall perinatal and neonatal outcomes were favorable for both groups. Therefore, efforts should be made to complete early fetal assessment in order to allow reduction during the first trimester.