For couples trying to have a baby, the No. 1 question that can be answered with a simple test is, Am I pregnant? No. 2 may soon be, Is it a boy or a girl?
For years, reliable answers could only be provided by invasive tests such as amniocentesis and chorionic villus sampling. Entrepreneurial genetic testing companies have sought an easier alternative. They claim they can identify a baby’s gender just weeks after conception by looking for signs of the male-only Y chromosome in a pregnant woman’s blood (if they find it, the baby must be a boy; if not, it’s a girl).
The problem is that such direct-to-consumer tests – which aren’t regulated by the Food and Drug Administration or the Federal Trade Commission – are frequently wrong. As we reported in a 2008 story, the biological principle behind the tests is sound, but the ability to actually find evidence of a Y chromosome in maternal blood varies widely. For example:
In a 2004 study, five medical centers in a National Institutes of Health consortium received identical blood samples from 100 women who were 10 to 20 weeks pregnant.
The centers used the same method to look for Y chromosomes in the maternal blood, but none was able to detect all of the 35 fetuses known to be male. According to the study, the detection rates ranged from 31% to 97%.
Now a team of Dutch researchers reports a new method for screening maternal blood and reports 100% success in determining a baby’s gender as soon as seven weeks after conception.
The study included 201 pregnant women whose blood was drawn between 2003 and 2009. The test produced conclusive results in 189 cases, and all of those results were correct. The findings were published in the January issue of the journal Obstetrics & Gynecology.
The idea behind the test isn’t simply to give parents extra time to start painting the nursery pink or blue. It’s to help screen for genetic disorders that are sex-linked. For instance, Duchenne muscular dystrophy and the blood clotting disorder hemophilia are tied to problems with the X chromosome and thus are almost always seen in males (since they only have one copy).
The blood test results made a difference for some of the women in the study. According to this report from Reuters:
Among the 156 women who underwent testing because of the risk of an X-linked disorder, the results allowed 41 percent to avoid further, invasive procedures to test for the disorder.
Another 27 women in the study were at risk of giving birth to babies with a genetic disorder called congenital adrenal hyperplasia, which causes girls to develop like boys. To prevent that from happening, the women began taking a steroid called dexamethasone as soon as they knew they were pregnant. But they were able to stop once the gender test revealed that their fetuses were male, according to Reuters.
But just because the test is accurate doesn’t mean it’s risk-free. Some prospective parents might take the results into account in deciding whether to continue a pregnancy, especially if they were hoping for a baby of a particular sex.
Bioethicist Arthur Caplan of the University of Pennsylvania said such tests are fraught with ethical problems. Even if doctors recommend the test to screen for a legitimate medical condition, it could “lead to abortions for non-medical reasons,” he told MSNBC.
With such concerns in mind, the Dutch researchers emphasized that “the test should be applied carefully in a clinical setting upon medical indication."
-- Karen Kaplan
Photo: Boy or girl? A blood test can tell you just a few weeks after conception, according to a new study. Credit: Los Angeles Times