It doesn't matter whether you orgasm or when you have sex. There's no way to control the sex of your baby, doctors say.

• When you're trying to conceive without assistance, the odds of having a boy or girl are about 50-50.
• The only way to control the sex of a fetus is through pre-implantation genetic screening.

Earlier this year, a Pakistani woman was so desperate to have a son, she reportedly hammered a nail into her own head based on advice from a "faith healer." While the story is extreme, it highlights the strong desire that many parents have to control the sex of their unborn babies.

But doctors say that unless you're undergoing IVF and doing pre-implantation genetic screening, there's no way to control the sex of your fetus, no matter what old wives' tales may claim.

"Science tells us that you basically have a 50-50 chance of having a boy or girl when conceiving," Dr. Sherry Ross, an OB-GYN, said.

Why you can't control your baby's sex

To understand why you can't control the sex of your baby, let's refresh basic biology. Females have an egg, which has an X chromosome. Males have sperm, which carry either an X or Y chromosome. If the egg is fertilized by an X sperm, it is XX, or biologically female. If it's fertilized by a Y chromosome, it's XY, or biologically male.

Although most people use the terms sex and gender interchangeably, being XX or XY doesn't necessarily determine whether your child will identify as a boy or a girl. It only determines their biological sex.

There are old wives' tales in many cultures that offer advice to parents who want to have a boy or a girl. The myths are varied and cover what to eat, the timing of sex, what position to do it in, and whether or not to orgasm. There's only one thing these myths have in common: They're not true.

"There is no medical evidence to suggest you can influence gender," Ross said.

There is one exception: If you undergo IVF and have your embryos genetically tested before implantation, you can select either a male or female embryo. This option is particularly important for people who are trying to avoid passing along diseases like sickle-cell anemia, which is mostly found in men.

Some assisted-reproduction clinics also offer sperm washing or sorting, which aims to separate X and Y sperm in order to increase your odds of having your desired sex. This technique, which is used with intrauterine insemination can increase your odds of having a girl to 60% and your odds of having a boy to 70%.

As we learn more about conception and reproductive health, the science of selecting a boy or girl is changing.

Past research has suggested that Y sperm, which produce males, swim faster. Because of this, scientists thought that having sex closer to ovulation could increase your odds of having a boy — in short, male sperm were more likely to win that race to the egg. However, a 2020 study found that there was no difference in the size or movement pattern between X and Y sperm.

Dealing with gender disappointment

It's normal for parents to want a specific gender and feel disappointed when they learn they're not having the little boy or little girl they envisioned. For most people, this feeling passes once the baby is born, Ross said.

While engaging with old wives' tales can be fun, it's best to keep expectations in check, Ross said.