To explore the clinical application value of high-throughput sequencing te-chnique in the screening of Down’s syndrome in fetal free DNA in pregnant women.

From Ap-ril 2013 to December 2019, a total of 1039 pregnant women who visited the genetic and prenatal diagnosis center of the first affiliated hospital of Zhengzhou University with non-invasive prenatal testing (NIPT) of trisomy 21 were selected. Quantitative fluorescent polymerase chain reaction (QF-PCR) and chromosome karyotype analysis were performed to verify the high-risk positive accuracy of trisomy 21 detected by non-invasive DNA.

Among 1039 pregnant women with a high risk of trisomy 21 in NIPT, chromo-somal karyotype analysis revealed that 886 cases were diagnosed as trisomy 21, and their positive predicti-ve value (PPV) was 85.27%, including 839 cases of standard Down’s syndrome karyotype (94.70%) , 28 ca-ses of translocation type (3.16%) , 14 cases of chimeric type (1.58%) , 5 cases of other abnormal chromosomes (0.56%) . There were 153 normal karyotypes with a false positive rate of 14.73% (153/1039) . The results of QF-PCR were consistent with the results of karyotype in a total of 1027 cases, with an accuracy rate of 99.32% (1027/1034).

The non-invasive DNA detection of fetal trisomy 21 has a positive predictive value of 85.27% which is a high, and thus can be widely used in the screening of birth defects of Down’s syndrome fetuses.

NIPT; Trisomy 21 high risk; Karyotype analysis; QF-PCR; Down’s syndrome