Evaluation of a two-step ultrasound examination protocol for the detection of major fetal structural defects

To evaluate a two-step screening protocol of ultrasound examinations (11-14 and 20-24 weeks) for the detection of major fetal structural defects.

Retrospective study in a private maternity hospital. Women with viable singleton pregnancies having both first trimester scan and anomaly scan at our department and subsequently delivered at our hospital were included. Major fetal structural defects were defined as those requiring medical or surgical treatment or those causing mental handicap.

A total of 3,902 pregnancies included 61 fetuses with structural defects (1.56%). Twenty-six (42.6%) were diagnosed in the first trimester and 29 (47.5%) in the second. Six anomalies were detected in the third trimester or after birth. Overall detection rate of the two-step program was 90.2%.

Detailed examination of fetal anatomy at 11-14 weeks resulted in the early diagnosis of about 40% of major structural defects.