Most current prenatal testing approaches like amniocentesis or chorionic villus sample include a certain degree of risk of miscarriage, but cell-free DNA testing relies on a blood sample, potentially changing what disorders can be looked for, Erin Biba at Wired writes. "Based on a small sample of a woman's blood, the cell-free fetal DNA test gives expectant mothers an earlier (and safer) look than ever at just who it is that's growing inside them," she adds.