The test analyzes fetal DNA found in the mother’s blood and can establish sex weeks earlier than other options.
A baby’s sex can be determined as early as seven weeks into pregnancy by a simple blood test. The test is highly accurate if used correctly, a finding that experts say is likely to lead to more widespread use by parents concerned about gender-linked diseases, those who are merely curious and people considering the more ethically controversial step of selecting the sex of their children.
The appeal of the test, which analyzes fetal DNA found in the mother’s blood, is that it can establish sex weeks earlier than other options, like ultrasound, and is noninvasive, unlike amniocentesis and other procedures that carry small risks of miscarriage. The finding came in a study published online Tuesday in The Journal of the American Medical Association.
The tests have been available to consumers in drugstore chains and online for a few years, but their use has been limited, partly because their accuracy was unclear. One company, which guaranteed 99.9 percent accuracy as early as five weeks into pregnancy, filed for bankruptcy after a lawsuit by scores of women whose tests showed the opposite sex of the baby they ended up having.
European doctors now routinely use the tests to help expectant parents whose offspring are at risk for rare gender-linked disorders determine whether they need invasive and costly genetic testing. For example, Duchenne muscular dystrophy affects boys, but if the fetus is not the at-risk sex, such tests are unnecessary. But doctors in the United States generally have not prescribed the tests because they are unregulated and medical labs are not yet federally certified to use them.
That and other aspects of the pregnancy landscape could change as a result of the new study. The journal study analyzed reams of research on fetal DNA tests — 57 studies involving about 6,500 pregnancies — and found that carefully conducted tests could determine sex with accuracy of 95 percent at 7 weeks to 99 percent at 20 weeks.
The study “has wide-reaching implications,” said Dr. Louise Wilkins-Haug, director for maternal-fetal medicine and reproductive genetics at Brigham and Women’s Hospital in Boston, who was not involved in the research. “Individuals need to be careful” to ensure that companies use rigorous laboratory procedures and support accuracy claims with data, she added.
