Pink or blue – now find out at 7 weeks of pregnancy

By Dr. Ananya Mandal, MDAug 10 2011

Now a simple blood test can determine a baby’s sex as early as seven weeks into pregnancy and is highly accurate if used correctly. Experts believe this will have a great impact on parents concerned about gender-linked diseases and those who are merely curious, as well as people considering the more ethically controversial step of selecting the sex of their children.

The test analyzes fetal DNA found in the mother’s blood. It can establish sex weeks earlier than other options, like ultrasound, and is non-invasive, unlike amniocentesis and other procedures that carry small risks of miscarriage.

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. Indeed, 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. However American doctors generally have not prescribed the tests because they are unregulated and medical labs are not yet federally certified to use them.

The findings of the new study published online Tuesday in The Journal of the American Medical Association reveals that carefully conducted tests could determine sex with accuracy ranging from 95 percent at seven weeks to 99 percent at 20 weeks.

Dr. Louise Wilkins-Haug, director for maternal-fetal medicine and reproductive genetics at Brigham and Women’s Hospital in Boston explained that the study “has wide-reaching implications”. “Individuals need to be careful” to ensure that companies use rigorous laboratory procedures and support accuracy claims with data, she added. She was not a part of the study.

The largest worry is women might abort fetuses of an undesired sex. In fact, several companies do not sell tests in China or India, where boys are prized over girls, and female fetuses have been aborted. A recent study in the journal Prenatal Diagnosis found that in some Asian-American groups, more boys than girls are born in ratios that are “strongly suggesting prenatal sex selection,” the authors said. Consumer Genetics, which sells the Pink or Blue test, requires customers to sign a waiver saying they are not using the test for that purpose. “We don’t want this technology to be used as a method of gender selection,” said the company’s executive vice president, Terry Carmichael.

Sex-determination tests are part of a new frontier of fetal DNA testing, which can be used to determine paternity and blood type, and is being used to develop early screening tests for genetic diseases like Down syndrome. The tests are not regulated by the Food and Drug Administration because they are not used for medical purposes, a spokeswoman said, but the agency is investigating the explosion of home genetic tests like these and genome-sequencing kits.

Dr. Diana Bianchi, executive director of the Mother Infant Research Institute at Tufts Medical Center in Boston and the lead author of the sex-determination report, said, “A very important aspect of the study is how this advances prenatal care.” Dr. Bianchi is conducting another study to “try to find out why people are buying these things and what are the consequences,” she said. “It’s very important to educate health care providers that pregnant women are buying these tests.”

“The test will not likely replace more invasive tests such as amniocentesis in the near future to detect such conditions as Down syndrome,” says Mary Norton, professor of obstetrics and gynecology and director of perinatal research at Stanford University School of Medicine. She also reviewed the research. That is because the test for Down syndrome has limitations. The most likely role for the test, at least for the near future, she says, would be “'to identify those women at high enough risk [of carrying a fetus with a birth defect] to go on to amnio.” However, by doing that, she says, it will spare many other women who are deemed not high risk the expense, stress, discomfort, and risk of amnio, she says.