Early anatomy ultrasound in women at increased risk of fetal anomalies.

OBJECTIVE

This study was designed to assess the accuracy of ultrasound anatomy screening before 17 weeks gestation in a population at high risk of fetal anomalies.

METHODS

Retrospective review of anatomy ultrasound examinations carried out between 12-17 weeks gestation in a high-risk population. Early sonographic findings were compared with the 18-22 week anatomy ultrasound, karyotype, echocardiogram and postnatal/postmortem results.

RESULTS

A complete anatomical survey was achieved in 68 of 101 screened fetuses (67%), with cardiac anatomy having the lowest completion rate (78/101; 77%). Anomalies were suspected on ultrasound in 23 fetuses. Four of these did not undergo pathologic examination but had clearly abnormal findings on ultrasound. Eighteen fetuses had a confirmed abnormal outcome. Sensitivity of early anatomy ultrasound was 83.3% (n = 15/18) and specificity 94.9% (n = 75/79). There were 3 false negative ultrasounds (16.6%: trisomy 21 with short humerus, choanal atresia and ventriculomegaly, and a ventricular septal defect). False positive rate was 4.0% (4 ventricular septal defects).

CONCLUSION

The high rate of visualization of anatomic structures between 12-17 weeks gestation allows for either early detection of fetal anomalies or parental reassurance in many cases. Subtle anomalies of the heart remain difficult to diagnose.