CHICAGO (AP) — 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.
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, typically done for medical
reasons, can detect gender starting at about 10 weeks.
The new analysis, published in Wednesday'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.
Tests that companies sell directly to consumers
were not examined in the analysis. Sex-detection tests using mothers' urine or
blood before seven weeks of pregnancy were not accurate, the researchers said.
Senior author Dr. Diana Bianchi, a reproductive
geneticist and executive director of the Mother Infant Research Institute at
Tufts Medical Center in Boston, called the results impressive. She noted that
doctors in Great Britain are already using such testing for couples at risk of
having children with hemophilia or other sex-linked diseases, partly to help
guide treatment decisions.
The research indicates that many laboratories have
had success with the test, but the results can't be generalized to all labs
because testing conditions can vary substantially, said Dr. Joe Leigh Simpson,
a genetics professor at Florida International University. He was not involved
in the study.
Dr. Lee Shulman, chief of clinical genetics at
Northwestern Memorial Hospital in Chicago, said the testing "isn't ready
for prime time."
He said his hospital doesn't provide the blood
tests, and doesn't offer more conventional techniques, including amniocentesis,
to women who have no medical reason for wanting to know their baby's gender.
"I would have a lot of difficulties offering
such a test just for gender identification. Gender is not an abnormality,"
Shulman said. "My concern is this is ultimately going to be available in
malls or shopping centers," similar to companies offering "cute"
prenatal ultrasound images.
Recent research found that increasing numbers of
women in India who already have daughters are having abortions when prenatal
tests show another girl, suggesting that an Indian ban on such gender testing
has been ineffective. The expense of marrying off girls has contributed to a
cultural preference there for boys.
Evidence also suggests that China's limits on one
child per couple and traditional preference for male heirs has contributed to
abortions and an increasingly large gender imbalance.
There's very little data on reasons for U.S.
abortions or whether gender preferences or gender-detection methods play a
role, said Susannah Baruch, a policy consultant for the Generations Ahead, an
advocacy group that studies genetic techniques and gender issues.
Consumer Genetics Inc. a Santa Clara, Calif.-based
company 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.
Carmichael said the company sells more than 1,000
kits a year. He said the company won't test blood samples unless women sign a
consent form agreeing not to use the results for gender selection.
The company also won't sell kits to customers in
China or India because of fears of gender selection, he said.
Medical techniques that can detect gender include
amniocentesis, usually done at around 16 weeks, using a needle to withdraw
fluid surrounding the fetus to identify abnormalities; chorionic villus
sampling, done at around the 10th week to detect abnormalities by examining
placenta tissue; and ultrasound, most accurate at around 13 weeks. The first
two methods can slightly increase risks for miscarriages.
Copyright 2011 The Associated Press.
