What it measures
A blood test in pregnancy that looks for Y-chromosome DNA from the baby in the mother's blood. Y-chromosome DNA points to a boy; none found points to a girl.
Why people test it
- Taken by parents who want to know the baby's sex earlier than a scan usually shows it.
- Used when a scan has not shown the baby's sex clearly.
Typical range
Reported as Y-chromosome DNA detected (a boy) or not detected (a girl), with no numbers. How labs word the result varies, and a result can come back inconclusive if too little of the baby's DNA is in the sample.
Finger-prick or vein?
Offered as a vein draw from the mother only. The baby's DNA is a small share of the DNA in her blood, so the test needs a clean sample of a good size.
The test can only be taken from a set week of pregnancy, which the provider states, as the baby's DNA needs time to build up in the mother's blood.