A RANDOMIZED TRIAL OF PRENATAL ULTRASONOGRAPHIC SCREENING - IMPACT ONTHE DETECTION, MANAGEMENT, AND OUTCOME OF ANOMALOUS FETUSES

OBJECTIVE: The objective of this randomized clinical trial was to test the hypothesis that ultrasonographic screening would significantly al ter perinatal outcome as a result of the antenatal detection of fetal congenital malformations. STUDY DESIGN: Pregnant women without a speci fic indication for ultrasonography were randomly assigned to have eith er two screening sonograms (15 to 22 weeks and 31 to 35 weeks) or conv entional obstetric care with ultrasonography used only as determined b y the clinical judgment of the patient's physician. The frequency of b irth defect detection in the screened and control populations was comp ared, as was the impact of discovery on pregnancy outcome. RESULTS: Ma jor congenital malformations occurred in 2.3% of the 15,281 fetuses an d infants in this study. Antenatal ultrasonography detected 35% of the anomalous fetuses in the screened group versus only 11% in the contro l population (relative detection rate 3.1; 95% confidence interval 2.0 to 5.1). Ultrasonography screening did not, however, significantly in fluence the management or outcome of pregnancies complicated by congen ital malformations. Specifically only 9 abortions were performed for a nomalies among 7685 fetuses in the screened group whereas 4 pregnancie s were terminated for fetal anomalies detected among 7596 control subj ects. Ultrasonography screening also had no significant impact on surv ival rates among infants with potentially treatable, life-threatening anomalies despite the opportunity to take precautionary measures such as delivery in a tertiary center. CONCLUSIONS: Ultrasonography screeni ng in a low-risk pregnant population had no significant impact on the frequency of abortion for fetal anomalies. Survival rates for anomalou s fetuses were also unaffected by screening.