Ultrasound detection of fetal anomalies in conjunction with first-trimester nuchal translucency screening: a feasibility study.

Abstract

The purpose of this study was to determine the effectiveness of a fetal anatomy survey in conjunction with first-trimester nuchal translucency (NT) screening ultrasound in an unselected pregnant population performed by sonographers. This was a prospective observational study of women presenting for NT screening for chromosomal defects. An anatomic survey was performed after a standardized protocol with a maximum scan time of 30 minutes. Three hundred twenty-five singleton fetuses (11+0 to 13+6 weeks) were examined and pregnancy outcome was available for 300 (92.3%) of cases. In 89 (24.6%) cases, transvaginal ultrasound was performed. The following fetal structures were seen in 95% of cases: cranium and intracranial anatomy, face, cord insertion, stomach, and all 4 limbs. The bladder was visualized in 89.5% of cases, the cardiac 4 chamber view in 84%, and the spine in only 45% of cases. Complete anatomy was seen in 109 (33%). Crown rump length greater than 55 mm and sonographer experience were important factors contributing to anatomic visibility. Of a total of 6 congenital defects in this cohort, 1 was detected in the first trimester (neural tube defect), 4 at the 18- to 20-week anatomic scan, and 1 postnatally. A complete anatomy survey was successful in 33% of first-trimester fetuses in a time-limited sonographer based screening program. Since some anomalies are not evident in the first trimester, the 18- to 20-week scan remains the gold standard.