Purpose: The aim of the study was to determine the detection rate of structural abnormalities at the 11-14 week ultrasound examination as a part of two-stage screening process in low-risk pregnancies.
Materials and methods: A total of 1085 consecutive low-risk pregnant women participated in screening by two-stage ultrasonography for the estimation of the sensitivity of the first and second trimester ultrasound scans in the detection of major anomalies as a part of routine screening.
Results: Of 1085 pregnancies, 21 (1.93%) fetuses had at least one major structural defect considered detectable by routine ultrasound screening; 14 (1.29%) were identified at early screening and an additional 5 (0.47%) at late screening. Two abnormalities were not detected prenatally, and data were obtained from the patients after delivery.
Conclusion: The majority of fetal structural abnormalities can be detected by sonographic screening at 11-14 weeks, but detailed fetal anatomic survey performed at 18-22 weeks should not be abandoned.