Many factors, both maternal (maternal blood transfusion, surgery, organ transplant, immunotherapy, neoplasm, or mosaicism) and pregnancy-related (vanishing twin, fetal demise, confined placental mosaicism, true fetal mosaicism, uniparental disomy, and polyploidy), can affect the results. NIPS is intended for screening purposes only, thus false negative and false positive results occur. This analysis does not assess the risk for other conditions, including but not limited to birth defects, open spine or ventral wall defects, intellectual disability, single gene disorders, or chromosomal abnormalities other than those listed above.