No abstract

United States and European consensus views differ on the place of routine ultrasound scans during pregnancy and the validity of such scans as screening tests for fetal malformations in the general population is still under debate. Four ultrasound laboratories from Obstetric and Gynecology departments of Belgian University hospitals and affiliated hospitals have conducted a prospective study from 1984 to 1989 to compare the anomalies discovered in ultrasonic screening of the fetus with the anomalies of the neonates. Of 16,370 pregnant women at normal risk for congenital anomalies attending the antenatal clinics of these hospitals, 16,072 have had at least one ultrasound screening for congenital anomalies (98.5%). Congenital anomalies, single or multiple and 'minor' or 'major', were clearly defined in order to allow comparisons. The excluded congenital anomalies were listed as defined in the Eurocat Register. A total of 381 fetuses (2.3%) were structurally abnormal. Of the 381, 154 were correctly detected by ultrasound (sensitivity 40.4%). Altogether 15,972 fetuses were true negatives (specificity 99.9%). Eight (0.05%) were false positive for congenital anomalies. The positive predictive value was 95.1% and the negative predictive value was 98.6%. Ultrasound diagnoses were correctly achieved before 23 weeks of gestation for 21% of the anomalies. The gestational age, operator and technical dependence of ultrasound screening for congenital anomalies is discussed.

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.

Ultrasound for routine fetal malformation screening has been polemical from its early beginning because of the very broad range of diagnosis rates disclosed, i.e. from 13% to 82%, average 27.5%. A review of available studies is proposed to assess objectively the efficacy of ultrasound, considering also economical, ethical and methodological aspects as influential factors for choosing a routine screening policy. The utility of fetal malformation diagnosis before birth is brought forward, including second opinion, karyotyping, poly-disciplinary case discussion prior to management. Method and material of reviewed studies considerably vary and might influence the sensitivity results, as the choice of the population sample and selection of pregnant women, gestation age at screening, distribution of malformation among systems or tracts, exclusion of some fetal malformation and the routine practice of autopsy. Efficiency of screening studies is compared, and among them Radius and Eurofetus studies. Average sensitivity is finally considered as satisfactory in the daily practice when operated by trained personnel. The importance of additional factors for successful screening are emphasized such as education, equipment quality and fetal ultrasound examination at different gestation age for a better understanding of natural history of fetal morphology.