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 to consumers for the past 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.
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The authors say the results suggest that 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.
The new analysis, published in today's Journal of the American Medical Association, involved more than 6,000 pregnancies.
Consumer Genetics of Santa Clara, Calif., sells an "early gender" blood test called "Pink or Blue" online for $25, plus $265 or more for laboratory testing.
It boasts of 95 percent accuracy, using a lab technique its scientists developed from the type of testing evaluated in the new analysis, said Terry Carmichael, the company's executive vice president.