Study points to a safer, better test for chromosomal defects in the fetus

"Our study is the first to show that almost all the information that is available from an invasive procedure is also available noninvasively from a simple maternal blood draw," says senior study author Richard Rava of Verinata Health.

Metaphase karyotypes -- pictures of chromosomes taken through the microscope -- have traditionally been used to detect abnormalities associated with developmental delay, intellectual disability, congenital defects, and autism. Recently, a method called a chromosome microarray, which uses molecular probes to detect gains or losses of DNA segments within chromosomes, has been shown to provide more detailed information than a metaphase karyotype. But both of these approaches require invasive procedures that involve removing tissue from the placenta or inserting a needle into the amniotic sac to collect fluid. As a result, they increase the risk of infection and could harm the fetus during pregnancy.

Massively parallel sequencing (MPS) of fetal DNA in the mother's blood offers a safer alternative for the detection of chromosomal abnormalities across the fetal genome. But it has not been known whether MPS is as accurate as chromosome microarrays. In the new study, Rava and his team found that MPS was capable of detecting a variety of chromosomal abnormalities as accurately as chromosome microarrays.

"Such a noninvasive test could have clinical utility in the near future, particularly for women who either have a medical contraindication or lack access to an invasive procedure," Rava says. "This work suggests an exciting future path toward routine noninvasive detection of abnormalities in the entire fetal genome."