There's the string test and all sorts of crazy ways to guess the sex of a baby, but new science is making it easy to know for sure in just the second month of pregnancy.
The National Institute of Health says that they can take a simple blood test, which takes cell free fetal DNA from the mother's blood. This means that they take the DNA that is circulating in the maternal bloodstream, rather than from something like bone marrow.
It's 95 percent accurate, which researchers say is still more reliable than any test using a urine sample.
Doctors say this could someday be a useful and certainly less invasive test than amniocentesis, which carries a risk for miscarriage.
Some parents want to know as soon as possible if it's a boy or a girl because there are some disorders linked to the sex of the baby.
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