Sonographic diagnosis of congenital anomalies during the first trimester.

Current ultrasound technology allows an examination of fetal anatomy and the detection of anomalies at 12-15 weeks. Studies assessing the accuracy of early sonographic diagnosis prior to 15 weeks of pregnancy were reviewed. In expert hands the detection rate is about 40 per cent for major extra-cardiac anomalies and 65 per cent for major cardiac defects. However, due to technical and practical limitations, sonographic assessment of fetal anatomy in the first trimester cannot replace the midtrimester scan and should be restricted to couples whose fetus is at increased risk for malformation.