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 125 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.