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.