Adoption of a non-invasive prenatal test (NIPT) in prenatal screening in Moscow: first results

The objective - To assess the effectiveness of including NIPT in the structure of prenatal diagnostics in Moscow. Material and Methods - Totally 5,181 pregnancies undergoing screening for fetal trisomy using NIPT during the period from 01.04.2020 to 30.09.2020 in Russia. According to the results of biochemical blood test, the patients were divided into two groups: group of high risk (cutoff >= 1:100) (n=208) and group of intermediate risk (cut-off 1:101 - 1:2500) (n=4,973). Patients at high-risk cell-free DNA (cfDNA) were offered an invasive procedure, followed by genetic analysis (cytogenetic or molecular karyotyping). Results - Among the analysed samples, 117 (2.3%) had a high risk of the following common fetal chromosome abnormalities by NIPT: trisomy 21 in 50 cases, trisomy 18 in 17 cases, trisomy 13 in 5 cases, and sex chromosome aneuploidy (SCA) in 22 cases. Additionally, rare autosomal trisomies and/or subchromosomal arrangements were revealed in 23 cases. We found associations between cfDNA concentration and high risk of aneuploidies (particularly trisomy 21) and fetal sex and between low fetal fraction (FF) and body mass index (BMI) as well as maternal weight. Additionally, a high risk of trisomy 21 was associated with the term gestation. Conclusion - The effectiveness of technological resources that are based on cfDNA testing for detecting abnormal fetal chromosome numbers and other chromosomal anomalies is high and reduce rates of false positive results. Therefore, NIPT should be more widely used as a first-line screening method.