News about simple maternal blood tests that can accurately identify the sex of a fetus, genetic disorders, and other traits early in the first trimester are reviving concerns about designer babies and an increased demand for abortion.

A report this week in JAMA finds that maternal blood tests can accurately identify the sex of a fetus as early as the seventh week of pregnancy. Such tests are already available, although their accuracy was uncertain. Last week a San Diego genetic testing company announced that it would market the first maternal blood test to detect Down syndrome in a fetus in the first trimester. The test, given the cute name MaterniT21, is expected to be available in the United States in late this year or early in 2012.

Even before the latest news about these tests, emotions have been running high in anticipation of them soon coming into wide use. Last December, researchers showed that they could do a genome scan of fetal DNA circulating in the mother’s blood, paving the way for prenatal blood tests for a wide range of...