Detection of fetal chromosomal anomalies: does nuchal translucency measurement have added value in the era of non-invasive prenatal testing?

Objectives The objective of this study is to determine what percentage of fetal chromosomal anomalies remains undetected when first trimester combined testing is replaced by non‐invasive prenatal testing for trisomies 13, 18, and 21. We focused on the added clinical value of nuchal translucency (NT) measurement. Methods Data on fetal karyotype, ultrasound findings, and pregnancy outcome of all pregnancies with an NT measurement ≥3.5 mm were retrospectively collected from a cohort of 25 057 singleton pregnancies in which first trimester combined testing was performed. Results Two hundred twenty‐five fetuses (0.9 %) had an NT ≥3.5 mm. In 24 of these pregnancies, a chromosomal anomaly other than trisomy 13, 18, or 21 was detected. Eleven resulted in fetal demise, and ten showed fetal ultrasound anomalies. In three fetuses with normal ultrasound findings, a chromosomal anomaly was detected, of which one was a triple X. Conclusions In three out of 25 057 pregnancies (0.01%), non‐invasive prenatal testing and fetal ultrasound would have missed a chromosomal anomaly that would have been identified by NT measurement. © 2015 John Wiley & Sons, Ltd. What's already known about this topic? Fetuses with an increased nuchal translucency (NT) are at an increased risk for chromosomal anomalies, structural defects, and genetic syndromes. Non‐invasive prenatal testing (NIPT) for trisomies 13, 18, and 21 has a higher sensitivity and specificity than first trimester combined testing. What does this study add? In 10.7% of pregnancies with an NT ≥3.5 mm, a chromosomal anomaly would initially be missed if first trimester combined testing was replaced by NIPT. Most chromosomally abnormal fetuses, however, showed fetal demise or were identified at the second trimester anomaly scan, indicating that NT measurement has a limited added clinical value in the setting of NIPT.