The diagnostic value of a detailed first trimester anomaly scan in fetuses with increased nuchal translucency thickness.

Objectives To assess the diagnostic value of an early anomaly scan in fetuses with increased nuchal translucency (NT) in the prediction of aneuploidy. Methods In this study we analyzed the data of pregnant women obtained at their first trimester screening in our unit. The detailed examination routinely includes measurement of NT and a scan for anatomical defects. For fetuses with an NT≥3.5 mm, the diagnostic power of early major sonographic findings (MSF) regarding abnormal karyotype was calculated. Results A total of 7352 first trimester examinations were screened. Two hundred and twenty-two fetuses with an NT≥3.5 mm were analyzed. The median gestational age was 12.5 weeks (range 11.0-14.6) and the median NT was 5.1 mm (range 3.5-15.3). MSF were detected in 51.8% of fetuses with increased NT. Among 115 fetuses with MSF, 91 were aneuploid, yielding a positive predictive value for aneuploidy of 79.1%. In the absence of MSF, the negative predictive value was 70.1%. The presence of MSF was significantly predictive for aneuploidy both in bivariate and multivariate regression analysis. Conclusion Our study underlines the importance of a detailed anatomical ultrasound in fetuses with increased NT, as MSF occurred frequently. However, the diagnostic value of MSF regarding aneuploidies appears to be moderate.