Thanks to a new test, checking for genetic abnormalities in a fetus is easier and less invasive — but there's a downside, says Nature News' Erika Check Hayden. Sequenom's new MaterniT21 Down syndrome test requires only a small sample of the mother's blood, and is only one of several similar tests expected to hit the market soon, Hayden says. While such tests spare women from amniocentesis or other invasive procedures, doctors say they pose other problems, Hayden says.