Can Cell-Free DNA Testing Suffice for Isolated Fetal Nuchal Translucency Between the 95th – 99th Centile? A Retrospective Analysis in A Centre in North India

Abstract All pregnancies with increased nuchal translucency (NT) > 95th percentile are traditionally offered invasive testing. This study aimed to determine whether cell-free DNA (cfDNA) could suffice in patients with an isolated increased NT between the 95th – 99th centile. A retrospectively analyzed prospective study was conducted in the Fetal Medicine Unit, Indraprastha Apollo Hospitals, New Delhi, between 2007 and 2021. Study criteria were singletons with increased NT between 95th – 99th centile without soft markers or structural abnormalities. cfDNA/follow-up was offered if patients declined invasive tests. Karyotyping was the primary genetic testing from 2007 to 2015, while microarray ± exome began thereafter. All outcomes were obtained over the phone or through patient records. There were 213 pregnancies with isolated findings of NT 95th – 99th centile. All were offered invasive testing, and 17 were lost to follow-up. In 196 cases with outcomes available, 7 (3.5%) had an abnormal genetic diagnosis. Four fetuses had trisomy 21, one trisomy 18, and two fetuses (1%) had other cytogenetic abnormalities. Five fetuses (2.5%) with chromosomal aneuploidy could be potentially detected with cfDNA. cfDNA may be a viable substitution to detect common aneuploidies in this clinical population. However, in 1% of cases, microdeletions may still be missed.