Early pregnancy blood test can reliably screen for gender: should it be used?

By Deborah Kotz, Globe Staff

Pregnant couples wishing to know the gender of their unborn baby can usually find out during a routine ultrasound performed around 20 weeks of pregnancy, but a review study published today in the Journal of the American Medical Association suggests that a test of the mother’s blood performed at seven weeks may be even more reliable.

The test -- which checks fetal cells in the mother’s blood for the Y sex chromosome, present only in male cells -- has been available in Europe for years but hasn’t found its way into routine medical practice in the United States. That could change given the new review, which analyzed 57 studies involving a total of 6,500 pregnancies and found that the tests were more than 95 percent accurate at determining gender at seven weeks of pregnancy. By 20 weeks, the accuracy was 99 percent.

But the researchers evaluated use of the test only in medical settings in foreign countries, not direct-to-consumer tests, which are currently the only way for pregnant women to get the test in the United States.

Given the validation of the blood test’s accuracy, experts say it’s only a matter of time before doctors begin offering it here -- and that could raise ethical concerns if couples terminate a pregnancy when the fetus isn’t the gender of their choice. In some countries like India and China, the percentage of girl babies has dropped precipitously in recent years, most likely because of gender selection in favor of boys.

“If couples can get the results earlier, that makes abortion less burdensome,” said Arthur Caplan, a bioethicist at the University of Pennsylvania. “A woman can take the test, and then take pills to terminate the pregnancy in the privacy of her home when it’s that early on. I would say gender selection is a bad reason to have an abortion, which is tough for a pro-choicer like me to admit.”

The blood test works by detecting fragments of fetal DNA that float through the mother’s bloodstream. Scientists can identify gender by looking for markers of the “Y” chromosome, which only appear in boys, and can assume the fetus is a girl if none is found.

While some American couples currently use ultrasound results as a reason to terminate a healthy pregnancy, the imaging test isn’t as accurate. Studies suggest it can determine fetal sex accurately about 86 percent of the time from 11 to 14 weeks and about 90 percent of the time beyond that.

More invasive techniques, like amniocentesis -- which involves drawing a sample of amniotic fluid via a needle inserted into a woman’s womb -- are nearly 100 percent reliable, but they pose a small risk of miscarriage and also can’t be performed early in pregnancy.

The blood test could provide some real medical benefits, said study co-author Dr. Diana Bianchi, a reproductive geneticist at the Mother Infant Research Institute at Tufts Medical Center, such as identifying sex chromosome-linked conditions -- in women known to be carriers -- like hemophilia, which affects only boys.

“In Britain, researchers have shown that using the Y-DNA test led to a reduction in amniocentesis and other invasive testing,” she said. The test could also help doctors determine the best treatment course in cases where the ultrasound indicates that the gender is ambiguous due to the structure or shape of the genitals.

Bianchi added that “the technique could be implemented in US labs pretty easily without high fees or a lot of infrastructure.”

Yet at the moment, testing is only offered through direct-to-consumer websites like Pink or Blue, which charges $179 for the basic kit that’s mailed directly to pregnant women and the testing of the blood sample that’s mailed back. Rush results can be had for $329.

“We have a 95 percent accuracy for our test, which we base on the number of customers applying for money back guarantees if the test didn’t accurately predict their baby’s gender,” said Terry Carmichael, executive vice president at Consumer Genetics, which manufacturers the Pink or Blue test. He added that several thousand people have bought the kits every year since 2005, when the product came on the market, and said he uses the same DNA-amplification technique identified in the study as being reliable.

Unfortunately, there’s no way for consumers to know for certain whether this test or others live up to their claims since -- like other genetic tests sold directly to patients online -- they’re not regulated by the US Food and Drug Administration.

Several years ago, Lowell-based Acu-Gen Laboratories promised that its Baby Gender Mentor blood test was “99.9 percent accurate” in detecting a fetus’s sex at five weeks and offered refunds to anyone who received wrong results. The company was forced into bankruptcy in 2009 after hundreds of women with false results filed class action lawsuits after they said they weren’t given any refunds.

Bianchi said four studies that collected DNA from urine samples found that that method was extremely unreliable, detecting the presence of a Y chromosome only 41 percent of the time. “They were worse than flipping a coin,” she said.