Accuracy of the mid-trimester ultrasound scan in the detection of fetal congenital anomalies in a reference center in Northeastern Brazil.

Objective: To assess the performance of a basic mid-trimester fetal ultrasound scan protocol for the diagnosis of congenital anomalies by calculating its accuracy, sensitivity, and specificity.

Methods: This longitudinal cohort study involved singleton pregnant women recruited at the mid-trimester fetal ultrasound scan through the postnatal evaluation of congenital anomalies. Pregnant women who underwent a routine mid-trimester ultrasound scan for fetal abnormalities at 20-24 weeks of gestation were enrolled in this study.