The days of wondering whether a child will be a boy or a girl could be numbered. According to a recent article, a simple blood test called cell-free fetal DNA can determine the gender of a baby just 7 weeks into a pregnancy. Which is much faster than amniocentesis – which can be given at about 16 weeks, or an ultrasound, which can be used a couple of weeks later. 

Dr. Diana Bianchi is a neonatal specialist at Tufts University. And she says the test looks for small pieces of the male sex chromosome in the mother's blood, which would mean she is carrying a boy. It’s accurate more than 95% of the time when they predict it’s a girl, and almost 99% when they say it’s a boy. And since many genetic diseases - like hemophilia - strike boys more often than girls, the test could spare new moms from invasive procedures like amniocentesis, which also raise the risk of a miscarriage.  

Unfortunately, knowing whether a baby is a boy or a girl has implications beyond medical tests, and whether to paint the nursery pink or blue. Dr. Mary Rosser is an obstetrician at the Montefiore Medical Center in New York. And she worries that knowing a baby’s gender that early might tempt parents to terminate the pregnancy if the baby’s not the sex they want. The test has been used in Europe for several years – and is about to become widely used in Canada. But because of the ethical implications, it may be some time before it’s available to parents in the U.S.