Many cases of congenital limb abnormalities referred for orthopaedic treatment are not diagnosed prenatally, despite routine ultrasound scanning. The authors aimed to study the detection rate and diagnostic accuracy of prenatal scans. Data concerning two groups of patients were collected. First, the authors followed-up 26,203 babies that had been scanned prenatally. Sixty had limb abnormalities; 15 of the abnormalities were detected prenatally (sensitivity 25%, 95% confidence interval 14%-36%). Second, the authors studied 67 cases from the Wessex Antenatally Detected Anomalies Register that had been identified prenatally. The diagnosis was confirmed postnatally in 56 cases (positive predictive value 84%, 95% confidence interval 75%-93%).