A baby is being held by an adult, and the baby looks directly at the adult.

A new approach to testing the genes of early-stage fetuses could radically alter the experience of pregnancy and parenting. And we'd better start thinking about it now-before hype, fear, and the polarized politics of abortion distort the discussion.

The technique being developed analyzes fetal DNA that is collected from women's blood as early as five weeks into a pregnancy. So-called "noninvasive prenatal diagnosis," or NIPD, may hit the market as a test for Down syndrome later this year. Soon after, refinements are likely that will allow identification of fetal genes at thousands of sites; two different research groups published papers claiming "proof in principle" of this prospect last December.

Because NIPD would be less invasive, less risky, and less expensive than the kinds of fetal gene tests now available, and because it relies on a simple blood draw so early in pregnancy, it is poised to become a prenatal game changer.

The fetal gene tests now offered are far from a walk in the park. For amniocentesis, a long needle is poked through your abdomen and uterus to extract amniotic...