OC02.04: First trimester nuchal translucency (NT) screening vs. NT Screening plus an anatomical survey: does it make a difference?

Since the introduction of 1 trimester NT Screening in North America following the FASTER trial, the debate among providers has been whether to limit the 1 trimester ultrasound evaluation to only measuring the crown–rump length (CRL) and NT. The purpose of this study was to ascertain the frequency of clinically important ultrasound findings derived from a detailed survey of fetal and uterine anatomy at the time of NT screening. All patients with a singleton pregnancy referred for NT screening between 11 weeks and 14 weeks of gestation underwent both transabdominal and endovaginal ultrasound evaluation of fetal and uterine anatomy. Power Doppler was used to examine the four-chamber and outflow tracts of the heart with a Thermal Index of 0.2 or less. All results were tabulated and grouped based upon whether the NT measurement was < 3 or 3 mm or greater. The study consisted of 2412 consecutive singleton fetuses. The CRL range was between 4.1 and 9.4 cm (mean 6.5 ± 0.9 SD), and was normally distributed. Fetal anatomy was imaged in 98% of fetuses. The NT was ≥ 3 in 1.4% (n = 34). The following table lists the distribution of findings categorized by the NT measurement. If a full anatomical study is performed in all patients undergoing NT screening, there is a significant yield of abnormal findings that have clinical relevance at the time of their identification. This would suggest that the protocol of only measuring the CRL and NT should be abandoned and a full study of the fetus and uterus should be undertaken at the time of NT screening. OC02.04: Table 1. Abnormal ultrasound findings