CHICAGO -- Boy or girl? A simple blood test in mothers-to-be can answer that question with surprising accuracy at about seven weeks, a research analysis has found.
Though not widely offered by U.S. doctors, gender-detecting blood tests have been sold online for a few years. Their promises of early and accurate results prompted genetics researchers to take a closer look.
They analyzed 57 published studies of gender testing done in rigorous research or academic settings, though not necessarily the same methods or conditions used by direct-to-consumer firms.
The authors say the results suggest blood tests like those studied could be a breakthrough for women at risk of having babies with certain diseases, who could avoid invasive procedures if they learned their fetus was a gender not affected by those illnesses.
But the study raises concerns about couples using such tests for gender selection and abortion.
Couples who buy tests from marketers should be questioned about how they plan to use the results, the study authors said.
The analyzed test can detect fetal DNA in mothers' blood. It's about 95 percent accurate at identifying gender when women are at least seven weeks' pregnant, more than one month before conventional methods.
Accuracy of the testing increases as pregnancy advances, the researchers concluded.
Conventional procedures, such as amniocentesis, typically done for medical reasons, can detect gender starting at about 10 weeks.
The new analysis, published in today's Journal of the American Medical Association, involved more than 6,000 pregnancies.
The testing used a lab procedure called PCR that detects genetic material, in this case, the male Y chromosome. If present in the mother's blood, she's carrying a boy, but if absent, it's a girl.