A simple blood test can determine a baby’s sex as early as seven weeks into the pregnancy, according to findings in The Journal of the American Medical Association reported by The New York Times. This test analyzes fetal DNA in the mother’s blood and can pinpoint sex much earlier than other options, including ultrasound. It’s also non-invasive. These tests have been available at drugstores and online for a few years but they haven’t been too popular, partly because of uncertainty over how accurate they were. But European doctors now routinely use these tests.