Which chromosomal abnormalities could lead to a false positive NIPT result?

Non-invasive prenatal testing (NIPT) is a screening method used to assess the risk of certain chromosomal abnormalities in the fetus by analyzing cell-free fetal DNA circulating in the maternal bloodstream. While it is a highly sensitive and specific method, there are circumstances that can lead to false positive results.

Placental mosaicism can occur when there are two distinct cell lines in the placenta, with one being genetically normal and the other exhibiting abnormalities. If the abnormal cell line is present in a significant proportion of the placental tissue, it may lead to a detection of chromosomal abnormalities, such as those associated with trisomy 21, which is characteristic of Down syndrome. This is why placental mosaicism can contribute to false positive NIPT results.

Additionally, maternal chromosome abnormalities can also affect NIPT results. For instance, if the mother has a chromosomal condition, such as a balanced translocation or a ring chromosome, it can introduce abnormal DNA sequences into the maternal plasma that may be incorrectly identified by the NIPT as indicating a risk for fetal abnormalities.

Therefore, the presence of both placental mosaicism and maternal chromosome abnormalities can lead to misleading results in NIPT, making the option that includes both scenarios the correct answer. This highlights