Screening for major structural abnormalities at the 11- to 14-week ultrasound scan.

OBJECTIVE: The purpose of this study was to examine the value of performing a detailed examination of the fetus as part of the routine 11 to 14 weeks' ultrasound scan in a 2-stage screening process for major structural defects in low-risk pregnancies.

STUDY DESIGN: This was a prospective study in 1148 singleton pregnancies at 11 to 14 weeks of gestation using a combination of transabdominal and transvaginal sonography to estimate the sensitivity of the first and second trimester ultrasound scan in the detection of major anomalies.

RESULTS: Seven of the 14 major anomalies were detected at the 11 to 14 weeks scan, and an additional 6 at the second trimester scan. The sensitivity of the early anatomic examination and the overall sensitivity of the 2-stage screening were 50% and 92.8%, respectively. Nuchal translucency was increased in 5 of the 14 (35.7%) abnormal fetuses and in 1 of the 4 cases (25%) with major heart defects.

CONCLUSION: Detailed, structured examination of fetal anatomy during the routine 11 to 14 weeks' scan can detect half of major structural defects in low-risk pregnancies.