<P> Non-invasive techniques include examinations of the woman 's womb through ultrasonography and maternal serum screens ( i.e. Alpha - fetoprotein ) . Blood tests for select trisomies ( Down syndrome in the United States , Down and Edwards syndromes in China ) based on detecting cell - free placental DNA present in maternal blood , also known as non-invasive prenatal testing ( NIPT ) , have become available . If an elevated risk of chromosomal or genetic abnormality is indicated by a non-invasive screening test , a more invasive technique may be employed to gather more information . In the case of neural tube defects , a detailed ultrasound can non-invasively provide a definitive diagnosis . </P>
which tests are noninvasive and performed to detect chromosomal abnormalities in the fetus
ultrasonography maternal serum screens non-invasive prenatal testing ( NIPT )