Gender selection: Can you try for a boy or a girl?

There are many theories bandied around suggesting you can plan a baby’s gender using different sex positions, timing or even the type of underwear the man wears.

But is there any substance to these claims or is it all urban myth?

Bupa’s National Medical Director and GP Dr Tim Ross explains the pros and cons of a few common tactics used to try for a boy or girl.

Sex positions

Dr Ross says many people believe different sex positions can predetermine a baby’s gender. This is based on the idea male sperm swim faster but die sooner and female sperm swim slower but survive for longer.

“The idea is if you have intercourse in a way where the sperm reaches the cervix quickly it’s more likely to be a boy, but if you have sex in a way where it takes longer for the sperm to get to the cervix you might have more chance of having a girl,” says Dr Ross.

For example, if a man enters the woman from behind the penis hits the cervix, so in theory there is an increased chance of the male sperm getting to the egg sooner. On the other hand, if a couple has sex in the missionary position, it’s thought to increase the chances of having a girl. Dr Ross says the sperm tends to slide down behind the cervix (in the missionary position) which can make the journey to the egg slower, so it’s thought the longer lasting female sperm has a better chance of making it.

Dr Ross says while many people swear this method is effective, the chance of getting the gender you’re after is still 50/50.

“You’ve got at least 20 million sperm in any one produce so the fact is it’s a matter of which ever sperm goes the right way at the right time and finds the egg,” says Dr Ross. “You can have a number of sperm at the egg at the one time and once one gets in it seals off and the others can’t get in.”


This theory, commonly known as the Shettles method, is also based on the idea that the male sperm are faster and the female sperm live longer.

“The idea is if you have sex earlier in your cycle you’re more likely to have a girl because the egg might not have been released yet and the sperm can last up to 48 hours,” says Dr Ross. “It’s based around the fact the female sperm survives for longer so it’s more likely there’ll be a female one left sitting around to meet the egg once it does come down the tube.”

For a boy, the idea is to have sex as close as possible to ovulation, in the hope the male sperm wins the race to the egg.

Dr Ross says the risk with trying this method is you need to know exactly when you’re ovulating or you could miss your chance. You might also reduce your chances of conceiving altogether by limiting the number of opportunities for egg fertilisation each cycle.

“You have to rely on having sex at only one time whereas most people just want to fall pregnant so they’re having sex right through the time of ovulation,” he says.

pregnant woman holding blue and pink bootees

The Whelan method

This theory, by scientist Elizabeth Whelan, suggests there are biochemical changes in a woman’s body at different points in her cycle which favour male or female producing sperm.

Unlike the Shettles method, Wheatlan suggests having sex four to six days before your basal body temperature goes up (when you’re about to ovulate) if you’re trying for a boy. Conversely, if you want to try for a girl she suggests having sex two to three days before ovulation.

Whelan claims this method has a 57% success rate, however there is little evidence to back these claims.

Keep it cool

Another theory, also based Dr Landrum B. Shettles’ method, is that if it’s a baby boy you’re daydreaming about then the man should try to keep his scrotum cool. This might mean no hot baths, switching briefs for boxer shorts, and perhaps even avoiding activities that you need to wear a wetsuit for.

This theory suggests when the scrotal temperature is too warm, the sperm count in general is reduced, but in particular the number of male sperm.

But before you paint the nursery, or buy blue booties, it’s important to know there is no solid evidence to back this theory.

The verdict

While we’ve all heard countless success stories, Dr Ross says there is no proven way to increase your chances of having either a boy or a girl.

“There’s no harm in trying different methods if you want to try for a particular gender, but there are no guarantees,” says Dr Ross. 

While it may be a 50-50 chance you’ll have a boy or a girl, if you have a healthy baby, either way that’s something to be celebrated.
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