ABSTRACT BACKGROUND: The prevalence of congenital abnormalities in general populations is approximately 3-5%. One of the most important applications of obstetric ultrasound is in detection of fetal structural defects. OBJECTIVE: To assess fetal structural anomalies diagnosed using ultrasound in the three trimesters of pregnancy. DESIGN AND SETTING: Retrospective cohort study at the Mário Palmério University Hospital of the University of Uberaba (Universidade de Uberaba, UNIUBE), from March 2014 to December 2016. METHODS: Ultrasound data at gestational weeks 11-13 + 6, 20-24 and 32-36 were recorded to identify fetal anomalies in each trimester and in the postnatal period. The primary outcome measurements were sensitivity, specificity, positive predictive value and negative predictive value for detection of fetal anomalies and their prevalence. RESULTS: The prevalence of anomalies detected using ultrasound was 2.95% in the prenatal period and 7.24% in the postnatal period. The fetal anomalies most frequently diagnosed using ultrasound in the three trimesters were genitourinary tract anomalies, with a prevalence of 27.8%. Cardiac anomalies were diagnosed more often in the postnatal period, accounting for 51.0% of all cases. High specificity, negative predictive value and accuracy of ultrasound were observed in all three trimesters of pregnancy. CONCLUSION: Ultrasound is safe and has utility for detecting fetal anomalies that are associated with high rates of morbidity and mortality. However, the low sensitivity of ultrasound for detecting fetal anomalies in unselected populations limits its utility for providing reassurance to examiners and to pregnant women with normal results.