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.

Key words: 11 to 14 weeks scan, Structural abnormalities, First trimester screening