RESUMEN
Introduction: Obstetric ultrasound is part of the screening to select the population at high risk of having a congenital malformation. Considering that fetal defects occur in approximately 2-4 out of every 100 live newborns, and are the cause of 35-40% of perinatal mortality in Chile, it is therefore justified to perform the second trimester ultrasound, which presents a high index prenatal screening (56%), with few false positives. Methods: A retrospective, cross-sectional and descriptive study was carried out, by reviewing 6,385 ultrasound scans, which were performed during one year (June 2020-June 2021), at the Regional Hospital of Talca, where 126 fetuses with suspected malformation were detected. Results: Of the total number of patients evaluated, a congenital malformation rate of 1.9% was detected, with cardiac malformations the most frequent, and diabetes mellitus the main risk factor. Conclusions: Antenatal ultrasound study is essential in the first and second trimesters of pregnancy, followed by a referral to an ultrasound committee, emphasizing early and interdisciplinary management. The frequencies found are similar to those reported in the international bibliography