Table 1.

Biological causes of false positive noninvasive prenatal test (NIPT) results (high-risk NIPT result, but normal fetal karyotype).

Placental/fetal causes

Confined placental mosaicism

In uterine demise of an aneuploid twin fetus (‘vanishing twin’)

Maternal causes

Maternal aneuploidy (e.g., 47,XXX)

Maternal mosaicism (e.g., 45X/46XX)

Maternal copy number variations (e.g., subchromosomal duplications or deletions, including 22q11.2 microdeletion carriers)

Maternal neoplasms (benign or malignant)

Prior organ transplanta

^aMay cause false positive result for male fetal sex.