Systematic analysis of the causes of NIPS sex chromosome aneuploidy false‐positive results

OBJECTIVE: To investigate the underlying causes of false positives in NIPT of fetal sex chromosomal aneuploidies using fetal cell‐free DNA from maternal plasma. METHODS: In the present study, we focus on a cohort of 23,984 pregnancy cases with NIPT. Karyotyping and FISH analysis were employed to verify the NIPT detected false‐positive results of fetal sex chromosomal aneuploidies, and a comparative CNV sequencing on positive and negative NIPT cases was uniquely performed to elucidate the underlying causes. RESULTS: A total of 166 cases (0.69%) were identified as fetal sex chromosomal abnormalities, while 84 cases were found to be false‐positive results possibly associated with maternal X chromosomal aneuploidies (n = 8), maternal X chromosomal structural abnormalities (n = 1), maternal CNVs (n = 4) as well as known placental mosaicism (n = 1). Furthermore, our study showed that the maternal chromosome CNV between 1–1.6 Mb was associated with false‐positive NIPT results in sex chromosomal abnormalities. CONCLUSION: Our research demonstrated the spectrum of factors causing false positives in NIPT of fetal sex chromosomal abnormalities based on a large cohort. The effective maternal CNV size cut‐off identified in our study could integrate into bioinformatics algorithms for reducing the false‐positive rate, however, further investigation is necessary to confirm this.