Clinical Utility of Nuchal Translucency Measurement in First-Trimester Ultrasound Screening in a Setting With First-Tier NIPT for Aneuploidy Screening

Objective To investigate the additional clinical value of nuchal translucency (NT) measurement at the first-trimester anomaly scan (FTAS) in a setting with first-tier non-invasive prenatal testing (NIPT).Method This nationwide prospective cohort study, part of the IMITAS study on FTAS implementation, included all pregnancies with increased NT (>= 3.5 mm) at FTAS, subsequently referred for detailed diagnostic scans at eight Dutch tertiary centers (Nov 2021-Nov 2022). Women with abnormal dating scans, abnormal NIPT before FTAS, or high-risk for fetal anomalies were not eligible for FTAS and received diagnostic ultrasound directly. The primary outcome was prenatal diagnosis of structural or genetic anomalies based on pre- and postnatal findings.Results FTAS was performed in 129,704 pregnancies, of which 230 (0.18%) had an increased NT. Anomalies were detected in 33.9% of these cases. Genetic anomalies included 76.8% aneuploidies, 14.3% SNVs, 8.9% CNVs; 39.3% beyond NIPT's detection scope. Trisomy 21/18 was diagnosed in 29.3% referred for increased NT without prior NIPT; 73.5% of these opted for termination. Anomaly prevalence increased with greater NT thickness.Conclusion NT measurement adds value in a national screening program including FTAS and NIPT. Prenatal counseling should address trisomies and other genetic abnormalities as a potential result of an abnormal FTAS, particularly when NIPT is declined.