Background: To explore the clinical value of secondary screening using noninvasive prenatal testing (NIPT) for women with critical-risk and low-risk pregnancies who had multiple of the median (MoM) abnormalities in serological screening.
Methods: NIPT was used to analyze fetal free DNA in the peripheral blood of 2,325 women with critical-risk pregnancies and 239 women with low-risk pregnancies with MoM abnormalities in serological screening. Based on NIPT results, women with high-risk pregnancies were recommended for amniocentesis for fetal karyotype analysis.
Results: Among 2,325 women with critical-risk pregnancies as determined by serological screening, NIPT indicated 15 high-risk pregnancies (11 cases of trisomy 21 and 4 cases of trisomy 18). Of the 15 patients, 1 case refused prenatal diagnosis. The other 14 cases underwent invasive amniocentesis for fetal karyotype analysis, and 13 cases of fetal chromosomal abnormalities were diagnosed, including ten cases of trisomy 21 and three cases of trisomy 18. NIPT of 239 patients with low-risk pregnancies but abnormal MoM showed one case with a high risk of trisomy 21, which was diagnosed as a false positive by amniotic fluid karyotype analysis, and one case with a high risk of trisomy 13 (stillbirth) that was diagnosed by karyotype analysis. A case of gender chromosome abnormality was diagnosed as aneuploidy by karyotype analysis.
Conclusions: The application of NIPT as a secondary screening for women with low- and critical-risk pregnancies as determined by serological screening but with MoM abnormalities will greatly reduce the number of invasive prenatal diagnosis procedures, significantly improve the rate and accuracy of fetal chromosomal abnormality detection.