End-result of routine ultrasound screening for congenital anomalies: the Belgian Multicentric Study 1984-92

Five ultrasound laboratories from Obstetrics and Gynecology departments of Belgian university hospitals or affiliated institutions conducted a prospective study from 1984 to 1992 in which the results of prenatal ultrasound examinations were compared to examination reports of the neonates. The results of the period 1984-89 (PI) have been published previously, and those of the period 1990-92 (PII) are presented here. Some very minor congenital anomalies, as listed and defined in the EUROCAT Register, were excluded. Of 26,147 pregnant women at normal risk for congenital anomalies, 25,046 had at least one ultrasound scan (96%). A total of 616 fetuses were structurally abnormal (prevalence 2.42%), and 685 abnormalities were recorded. The sensitivity of the ultrasound test was 40.4% in PI and 51.1% in PII for abnormal fetuses (p < 0.05), and 45% (PI) and 64% (PII) for abnormalities (p < 0.01). The specificity was 99.9% and the positive and negative predictive values were 94.2% and 98.6%, respectively; these values did not differ significantly between the two periods. The sensitivity for the detection of anomalies before 23 weeks increased from 21% in PI to 41% in PII, indicating an improvement in the early detection of fetal abnormalities.