[Clinical value of routine non-invasive prenatal testing for the screening of non-target chromosomal abnormalities]

To assess the value of non-invasive prenatal testing (NIPT) for the identification of sex chromosome aneuploidies (SCAs), copy number variants (CNVs) and rare autosomal trisomies (RATs).

A total of 11 429 women with singleton pregnancy in Ningbo area were screened by NIPT. 106 women were subjected to invasive prenatal diagnosis due to high risk of chromosomal abnormalities other than 21, 18 and 13 aneuploidies. All cases were followed up for pregnancy outcome and postnatal status.

Sixty-six women were signaled by NIPT for fetal SCAs, among whom 54 were willing to undergo prenatal diagnosis. Eighteen cases of fetal SCAs were verified as true positives and 4 were suspected positives, which yielded a positive predictive value (PPV) of 33.3%. Half of the women decided to continue their pregnancy. Forty women were signaled by NIPT for fetal CNVs, among which 32 underwent prenatal diagnosis. 19 cases of fetal CNVs were verified as true positives and 3 cases were suspected positives, which yielded a PPV of 46.8%. All women with pathological or possibly pathological CNVs decided to terminate their pregnancies. Thirty-one women were signaled for with fetal RATs. Two fetuses were confirmed to harbor mosaicism trisomies by prenatal diagnosis, and 1 case was suspected to be positive, which yielded a PPV of 9.7%. All of the three women have decided to terminate their pregnancy.

In addition to aneuploidies of target chromosomes, NIPT also has important value for the detection of SCAs and CNVs. The results can help to further reduce birth defects. Nevertheless, in view of its low PPV, pregnant women with positive result still need appropriate genetic counseling and prenatal diagnosis to avoid unnecessary induced labor.