504: Reduction in dichorionic twin pregnancy, a retrospective cohort study

To assess the outcome of dichorionic twin pregnancy managed expectantly versus those reduced to singletons. We studied in a retrospective study consecutive cases of twin pregnancies that were reduced to singletons in the Netherlands between 2000-2010. The reductions were performed between 10-23 weeks by transabdominal injection of KCL. The outcome of these pregnancies was compared to twin pregnancies that were collected from a previous RCT (AMPHIA ISRCTN 40512715) and to singleton pregnancies born in 2008 retrieved from the Dutch perinatal registration. The two groups were compared for median gestational age, pregnancy loss <24 weeks, preterm delivery <32 weeks, neonatal birth weight and number of stillbirths. Statistical tests were performed in SPSS 18. Mann-Whitney U test was use to compare mean neonatal birth weight and Chi Square test was used to compare delivery rates <24 and <32 weeks and number of stillbirths. We identified 98 twin pregnancies that were reduced to singletons, 91 for congenital anomalies and 7 for social indications. Median gestational age for these pregnancies was 39.0 weeks (SD 3.8). Ongoing twin pregnancies had a median gestational age of 37.0 weeks (SD 5.8). Pregnancy loss <24 weeks was significantly higher in the reduction group compared to ongoing twins (6.6% vs 2.5% respectively). For delivery <32 weeks there was no significant difference between the two groups (15.4% vs 11% respectively). The median birth weight at birth of the first child was 3120 gram in the reduction group and 2500 gram in the ongoing twin group (p-value 0.00). In the reduction group the percentage of stillbirths was significantly higher compared to the ongoing twin group (9% vs 2%). In this study, selective reduction of twin pregnancy to singletons gave a higher risk of pregnancy loss than in ongoing twins, but it significantly improved gestational age and neonatal birth weight. Women opting for selective reduction on social indication should realise there is a significant risk in losing the complete pregnancy before making this decision. Tabled 1