Timing of pregnancy may predict baby's gender

There's still no way to choose the sex of your baby, but Dutch researchers say they have found a way to better predict whether an expectant mom is having a boy or girl by looking at the timing of her pregnancy. "Some people really want one or the other," says Patrick Weix, MD, obstetrician and gynecologist on the medical staff at Baylor Medical Center at Irving in Texas. "We obviously don't make any promises, but we just do our best to see if we can tell accurately what they're having," says Dr Weix.

A new study by Dutch researchers found a mother may be able to look at the timing of her pregnancy to predict whether it's a boy or girl well before an ultrasound can.

"In the study, if it took the woman longer to get pregnant then they actually had a higher percentage of boys being born," notes Dr Weix.

More specifically, the researchers found that for couples conceiving naturally, each additional year of trying to get pregnant was associated with a four percent increase in the likelihood of having a boy. Why? The answer is complicated, but it has to do with the differing swim rates between the male and female sperm.

"If there is a difficulty, if this becomes sort of the rate-limiting step, if there's a little bit of a hurdle than it's going to favor the male sperm," Dr Weix says.

Previous studies have also supported the results of this most recent research. Experts remind parents that a four percent increase in the likelihood of having one sex or the other is still very small.