What does a false positive result in Non-Invasive Prenatal Screening (NIPS) potentially indicate?

A false positive result in Non-Invasive Prenatal Screening (NIPS) may indicate confined placental mosaicism. This condition occurs when there are two genetically different cell lines present within the placenta, which can lead to discrepancies in the genetic material being analyzed in NIPS. Since NIPS evaluates cell-free fetal DNA present in maternal blood, the presence of abnormal placental DNA can give rise to a false positive result for fetal aneuploidy, even when the fetus itself is genetically normal.

Confined placental mosaicism can affect the accuracy of NIPS because the placental cells may not reflect the fetal genetics accurately. Thus, a false positive result could suggest that additional testing, such as amniocentesis or chorionic villus sampling, may be necessary to clarify the status of the fetus and determine whether there are any true genetic abnormalities.

While maternal obesity, advanced maternal age, and unilateral renal agenesis can be associated with various pregnancy complications or risks, they are not directly linked to the occurrence of false positive results in NIPS. Maternal obesity may affect the quality and quantity of fetal DNA available for testing, but it does not specifically cause false positives in the same way that confounding placental conditions, such as confined placental