Blood Test Determines Gender at Seven Weeks

by Kazue Koyanagi

male symbol on dna fragments"Are we having a boy or a girl?"

"Do we have any inherited disorders?"

"How can we find out if anything's wrong early on?"

The answers to these questions can be discovered as early as seven weeks gestation. All it takes is a peek at small pieces of your baby's DNA floating in mom's blood. Recent research has moved these tests from the realm of science-fiction into the reality of prenatal care.

Free Cell DNA Testing

This new testing method, called free cell DNA, promises to give a closer look into the health (and sex) of your baby early in pregnancy.

Fragments of fetal DNA (cell free DNA), seep into the expectant mother's bloodstream through the placental wall. Researchers have noted them as early as five weeks after conception. These fragments can be analyzed and used for prenatal genetic testing.

Free cell fetal DNA testing is routinely used in France, Spain, and the Netherlands. This noninvasive alternative to amniocentesis can determine gender and sex-related problems.

What Can You Learn from Fetal DNA

Parents can screen early in the pregnancy to find out if the baby's a boy or girl and for disorders linked to a particular gender.

Free cell DNA testing can determine:

  • Paternity
  • Rh blood group typing
  • Baby's gender
  • Hemophilia
  • Duchennes muscular dystrophy
  • Congenital adrenal hyperplasia

Within the next few years, scientists speculate that free cell DNA testing will be offered for the diagnosis of Down's syndrome, Cystic Fibrosis and Beta-Thalassemia. As the technique improves, the goal is this test can help with the diagnosis of other conditions as well.

Free Cell DNA Compared with Traditional Tests

  Free Cell DNA CVS Amniocentesis
When is test performed? throughout pregnancy during weeks 10-13 during weeks 14-24
Is test invasive? no yes, cells are taking from the placenta yes, amniotic fluid is removed with a syringe
Risk to pregnancy none 1-3% risk of miscarriage 1% risk of miscarriage
Accuracy determining gender at 7 weeks, male baby 95.4%, female 98.6% at 10-13 weeks, 100% at 14-24 weeks, 100%

When Baby's Sex Matters

Your baby's genitalia can be spotted on an ultrasound as early as 11 weeks, but predictions miscall the gender about 40% of the time. By 18-22 weeks, when most "big" ultrasounds take place, your baby's sex can be accurately spotted barring the unforeseen. The fact is, people don't like to wait that long.

"We would love to have a girl (this is our first) but would be over the moon if we're expecting a boy as well. It's so hard to stay gender neutral, though! Ugh! I hate the gender waiting game!" ~Ashlynp1109, Pregnancy.org member

But curiosity isn't the only reason for earlier gender testing. Certain genetic disorders are linked to the X-chromosome, so they overwhelmingly affect males, whose XY sex chromosomes mean they lack the "backup" X that women have.

Right now, families at risk for these disorders can opt to have amniocentesis or chorionic villus sampling. Both tests carry a small risk of miscarriage.

Blood tests could help prevent more invasive procedures. Diana W. Bianchi, a reproductive geneticist at Tufts University School of Medicine in Boston, Massachusetts says, "A non-invasive blood test (like free cell DNA) would reduce such testing by 50% because moms carrying female babies wouldn't need to worry."

Blood tests could target prenatal treatments. Another disorder, Congenital Adrenal Hyperplasia, or CAH, disrupts hormone balance. Female fetuses take on masculine traits. Moms carrying a baby with CAH take steroids during their pregnancies. If fetal sex were known earlier, the moms carrying male fetuses with CAH would be able to skip the steroids and their unpleasant side effects.