Limitations of using first-trimester nuchal translucency measurement in routine screening for major congenital heart defects

Objective To evaluate the effectiveness of nuchal translucency (NT) measure ment in screening for major congenital heart disease (CHD) in chromosomally normal fetuses. Design A population based cohort study of all women having fetal NT measure ment at 10-14 weeks of gestation in an unselected population over a 3-year period. The outcome measure was the identification of major CHD in chromoso mally normal pregnancies either antenatally or postnatally. Results Major defects of the heart and gr eat arteries were identified in 2 6 out of 7339 pregnancies (prevalence 3.5 per 1000 pregnancies). Out of 26 cases, only four (sensitivity 15.4%, 95% CI 4-35) were in the group of 258 pregnancies (3.5%) with increased NT of greater than or equal to 2.5 mm. Th e prevalence of major CHD increased from 3.1 per 1000 for NT < 2.5 mm to 50 per 1000 for NT <greater than or equal to> 3.5 mm (likelihood ratio of 14. 1, 95% CI 4.2-47.9). The positive and negative predictive values for NT gre ater than or equal to 2.5 mm were 1.6% and 99.7%, respectively. Conclusions The prevalence of major CHD in this study was 3.5 per 1000, sug gesting that ascertainment of CHD in our study population was thorough. Fet uses with NT measurements greater than or equal to 3.5 mm have a significan tly increased risk of major CHD, and this identifies a subgroup of high-ris k patients in whom early fetal echocardiography would be advocated The late sensitivity of NT for major CHD in the general population, however, indica tes that NT cannot be relied on as the sole or major screening tool for thi s condition as previously reported.