Objective: To study the influence of maternal sex chromosomal abnormalities on the prediction of fetal sex chromosome abnormalities (SCAs) by non-invasive prenatal testing (NIPT).
Methods: Thirty-six pregnant women with a prediction for fetal SCAs by NIPT were verified as false positive after prenatal diagnosis using amniotic fluid samples. With informed consent, these women were subjected to chromosomal karyotyping or copy number variations (CNVs) analysis through high-throughput sequencing.
Results: Sex chromosomal abnormalities were found in 8 women, which yielded an abnormal rate of 22.22% (8/36). Among these, 3 had sex chromosome aneuploidies (47, XXX), 4 had sex chromosome mosaicisms, and 1 carried structural chromosomal abnormalities. Reanalysis of the results of NIPT were consistent with the maternal CNVs by large. With the ratio of cffDNA (ChrX)/cffDNA was more than 2, 6 of the eight women were found to harbor sex chromosome abnormalities, and the fetal karyotype was normal. However, with a ratio of less than 2, only 2 of the 38 pregnant women had sex chromosome abnormalities, and 10 of the fetuses were confirmed as positive.
Conclusion: The presence of maternal sex chromosomal abnormalities can greatly influence the result of NIPT, which may also be an important reason for false prediction for fetal SCAs by NIPT. When NIPT indicates abnormal SCAs, it is necessary to analyze maternal sex chromosomes. The ratio of cffDNA(ChrX)/cffDNA may help to determine the source of abnormal signals.