Non-invasive prenatal testing (NIPT) for aneuploidy using cell-free DNA in 
maternal plasma is revolutionizing prenatal screening and diagnosis. We review 
NIPT in the context of established screening and invasive technologies, the 
range of cytogenetic abnormalities detectable, cost, counseling and ethical 
issues. Current NIPT approaches involve whole-genome sequencing, targeted 
sequencing and assessment of single nucleotide polymorphism (SNP) differences 
between mother and fetus. Clinical trials have demonstrated the efficacy of NIPT 
for Down and Edwards syndromes, and possibly Patau syndrome, in high-risk women. 
Universal NIPT is not cost-effective, but using NIPT contingently in women found 
at moderate or high risk by conventional screening is cost-effective. Positive 
NIPT results must be confirmed using invasive techniques. Established screening, 
fetal ultrasound and invasive procedures with microarray testing allow the 
detection of a broad range of additional abnormalities not yet detectable by 
NIPT. NIPT approaches that take advantage of SNP information potentially allow 
the identification of parent of origin for imbalances, triploidy, uniparental 
disomy and consanguinity, and separate evaluation of dizygotic twins. Fetal 
fraction enrichment, improved sequencing and selected analysis of the most 
informative sequences should result in tests for additional chromosomal 
abnormalities. Providing adequate prenatal counseling poses a substantial 
challenge given the broad range of prenatal testing options now available.