Reported Biologic Causes of False Positive and False Negative Cell-free DNA Results.

Causes of false positive results:
   Confined placental mosaicism (placenta aneuploid, fetus euploid)30
   True fetal mosaicism
   Death of a twin in utero
   Maternal incidental findings
       Copy-number variant
       Chromosome abnormality
       45,X or 47,XXX
       Mosaic trisomy for an autosome
       Leiomyoma
   Cancer
       Hodgkin’s or non-Hodgkin’s lymphoma (most common)
       Other lymphomas (follicular, cutaneous T cell)
       Breast cancer
       Colorectal cancer
       Chronic myelogenous leukemia
       Multiple myeloma
       Other cancers (neuroendocrine, angiosarcoma, small-cell carcinoma)
   Previous organ or bone marrow transplant from male donor
   Medical condition or treatment affecting quality of circulating DNA
       Autoimmune disease
       B12 deficiency
       Intrahepatic cholestasis of pregnancy

Causes of false negative results:
   Low fetal fraction
       Maternal obesity
       Multiple gestation causing low fetal fraction per fetus
       Maternal medical condition or treatment affecting quality of circulating DNA
       Certain fetal chromosomal aneuploidies (e.g., triploidy)
   Confined placental mosaicism (placenta euploid, fetus aneuploid, or mosaic)

False positive results are much more common than false negative results (88% vs. 12%)