INTRODUCTION: Few studies have examined patients' understanding of prenatal ultrasounds (US). Our primary aim was to describe women's understanding of abnormalities detectable by midtrimester fetal anatomy scan. Our secondary aim was to determine if differences in the results varied with maternal demographics to identify subgroups who may benefit from additional counseling. METHODS: This was a cross-sectional survey of English-speaking patients presenting for a midtrimester fetal anatomy scan at a tertiary care teaching hospital. Patients were recruited prior to their US and if consent was obtained they completed a pre-US survey. The survey obtained demographic information and assessed knowledge of US detectable anatomic abnormalities by seven questions. Comparison between groups was performed by Wilcoxon rank sum test, Spearman rank correlation, and bivariate linear regression as appropriate. RESULTS: 123 participants were recruited, 117 consented, and 116 completed surveys. A median of 43% [Interquartile Range 14-71%] of questions were answered correctly. Number of correct responses was found to correlate inversely with income <$50,000/year (P<0.0001), education less than Bachelor’s Degree (P<0.0001), age (P=0.001), and African American race (P<0.0001) in bivariate analyses. CONCLUSION: Patients with lower income, less education, younger age, and African American race have less knowledge about fetal anomalies detected via a midtrimester ultrasound. These data suggest that these women may benefit from additional counseling regarding the function of ultrasound as a medical test with the purpose of detecting fetal anomalies early in pregnancy.