To assess fetal characteristics and post-natal outcomes of fetuses diagnosed prenatally in the contemporary era with hypoplastic left (HLH) and hypoplastic right heart (HRH) This was a retrospective single center study from 2013-2022. Data were collected from our fetal cardiology database and included diagnosis (HLH or HRH), pregnancy outcome (interruption, fetal demise, or live birth), gestational age at diagnosis and delivery, non-cardiac and genetic anomalies, family history, postnatal outcome from those who completed the procedures (birth to first procedure, first to 2nd and 2nd to third procedures) and complications of extracorporeal membrane oxygenation (ECMO), postoperative tachyarrhythmia and G-tube placement. Measures were summarized as frequency (categorical variables) and mean± SD (continuous variables) and compared using two sample t-tests and Fisher’s exact tests. We identified 183 fetuses with SVS: 133 HLH, 50 HRH (figure, table). Overall, 12 (7%) of pregnancies were interrupted and 7 (4%) were stillborn; 161 were liveborn. Twelve percent of pregnancies had a family history of congenital heart disease and 30% of those undergoing prenatal genetic testing (n=67, 42%) had abnormalities; results did not differ between HRH and HLH. Similarly, there were no differences in gestational age at delivery, sex, or fetal losses, however birth weights were significantly lower in HRH (2.7 (0.6) than HLH (3.1 (0.6), p=0.005. From birth to first procedure (n=159), 11 died (9 HLH), 5 received transplants and 143 were palliated. From 2nd to 3rd procedure (n=122) significant differences existed between HLH and HRH (p< 0.001) 9 died (all HLH) 6 received a cardiac transplant, and 107 (80 HLH) underwent stage 2 palliation. Similarly for the 70 who have undergone third stage, 2 died (both HLH), 12 were transplanted and 53 were palliated. Even in the current era, patients with single ventricles remain medically fragile. Overall mortality was 14% and 20% received cardiac transplantation. Genetic testing occurs in only a small proportion of single ventricle fetuses.View Large Image Figure ViewerDownload Hi-res image Download (PPT)