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BEIJING, Aug. 10 (Xinhuanet) -- A new technology can tell pregnant women whether they're having a boy or girl as early as seven weeks into a pregnancy -- months earlier than usual, according to media reports Wednesday.
The technology works by detecting "cell-free fetal DNA," or DNA from the fetus, which floats freely in a pregnant woman's blood, said author Diana Bianchi of the Tufts University School of Medicine in Boston.
Her analysis of 57 studies from peer-reviewed medical journals showed that these blood tests, common in Europe but not in the U.S. can reveal a fetus' sex only a week or two after a pregnant woman misses her period.
Women usually learn the fetus' sex through an ultrasound at 18 to 20 weeks.
The technology will help families worried by having a child with rare genetic disorders that typically affect only boys, such as hemophilia or a type of muscular dystrophy, said Joseph Biggio, director of the Trimester Genetics Screening Clinic at the University of Alabama-Birmingham.
If they're having a girl, however, they can stop worrying, he added, and avoid further invasive tests, which can provide a definitive answer about genetic disorders, but also increase the risk of miscarriage.
Women who learn they're carrying boys would still need a definitive test, such as an amniocentesis, to find out if their fetus is affected.