Choosing the sex of your baby: Are the old wives' tales true?

From having your partner wear boxers to putting a nickel in your mouth during conception, legend has it that you can influence your baby's sex. But the truth is, while certain steps can increase your chances of getting pregnant, there's no evidence you can control whether you have a girl or a boy. Unless you use certain in vitro fertilization techniques, the odds are always pretty much 50-50. Still, it can be fun to see what folk wisdom says about choosing your baby's sex.

Boy or girl
Photo credit: © Thinkstock / Hemera

Can what you eat predict your baby's sex?

According to old wives' tales, yes. But scientifically, no.

Though the X and Y chromosomes in sperm ultimately determine whether you have a girl or boy, some myths say diet can influence a woman's body chemistry, making you more likely to conceive one or the other. Based on legend, a wide variety of foods can do the trick.

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If you want a boy...

  • Eat more veggies.
  • Opt for foods high in potassium, such as bananas and white beans.
  • Stick with salty snacks such as pretzels and chips.
  • Cut back on eggs and dairy products.
  • Drink coffee before sex.

If you want a girl...

  • Give in to your chocolate craving, or just eat sweets in general.
  • Eat foods high in calcium and magnesium, such as fish, spinach, and yogurt.

Sometimes, beliefs about diet contradict each other. For example, some people say that eating more meat raises your chances of having a boy, while others advise you to eat less meat to get the same result.

The truth, however, is there's no scientific proof food has any sway over your baby's sex. Even the limited research suggesting a link between the two can't prove cause and effect – just that there could be a relationship.

Can having sex around the moon phases influence whether you have a boy or girl?

It's true that the timing of intercourse does influence whether you can get pregnant, but it can't influence your baby's sex.

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However, many of us still like to check our horoscope, so is it any surprise that superstition and folklore have led to theories about when to make love if you want to pick your baby's sex?

Word has it:

If you want a boy...

  • Sleep together when there's a quarter moon in the sky.
  • Have sex at night.
  • Mark your calendar – more boys are conceived on odd days of the month.
  • Follow the compass – one BabyCenter parent swears that pointing the woman's head north while making love guarantees a boy.

If you want a girl...

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  • Hit the sheets when the moon is full.
  • Make a date in the afternoon.
  • Get together on the even days of the month.

Another sex-selection myth is related to ovulation, or when your ovary releases an egg. The story goes that having sex close to your ovulation date means you're more likely to have a boy, since sperm containing a Y chromosome are faster swimmers – essentially, they'll get there first. For a girl, you're supposed to space the timing out a bit more.

So, what's the real deal? It's true that sleeping together during your “fertile window” – the five days before ovulation and the day you ovulate – can increase the chances of getting pregnant. But in general, the dates and times of intercourse have no influence over whether your baby is a boy or girl.

Can temperature affect your baby's sex?

It depends what you're talking about temperature-wise.

Some old wives' tales have to do with body temperature. For a daughter, they say a man's testicles are supposed to be cool before you have sex. For a son, it's best if they are warm. The idea plays into a common belief about boxers versus briefs: Wearing boxers keeps the area nice and breezy, meaning you're more likely to have a girl. Donning tighty-whities, on the other hand, generates heat, tipping the balance in favor of a boy.

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The truth is, scrotal temperature doesn't affect the sex of a baby. It can, however, influence sperm production. Several studies have found that men who wear boxers have higher sperm counts and sperm concentration than those who wear other types of underwear. This could be because boxers keep the genitals cooler.

If you're talking about temperature in terms of the weather, it may be a different story. Some studies have found there are more girls born in higher-latitude areas, which generally have colder temperatures. (Think Sweden vs. Greece.) Other studies suggest that the season at the time of conception may play a role, too.

And then, there's climate change. According to a handful of analyses, natural catastrophes may mean more girls, while warmer days caused by global warming may tilt the odds slightly towards boys.

Other old wives' tales about conceiving a boy or girl

Quite a few folktales about sex selection revolve around the best way to make love.

If you want a boy...

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  • Make love standing up.
  • Try the rear-entry position.
  • Have deeply penetrative sex.
  • Focus on her pleasure – make sure the woman climaxes.
  • The man is supposed to initiate sex.

If you want a girl...

  • Give the missionary position a go.
  • Try spooning!
  • Make love with the woman on top.
  • Focus on his pleasure – the man needs to orgasm but the woman isn't supposed to.
  • Let the woman initiate sex.
  • Try to remain relaxed during sex.

And still more tales defy categorization. One says that if you want to conceive a boy, the woman can hold a nickel in her mouth during sex. Another story says that the baby's sex is determined by which partner is dominant in the relationship at the time of conception.

As with the other legends, there's no evidence sex is determined by relationship dynamics, sexual positions, or coins. The chances of giving birth to a boy or a girl are always about 50-50, unless you select the sex during in vitro fertilization.

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Those of you who are truly serious about sex selection should be sure to see our article on what the scientists say.

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BabyCenter's editorial team is committed to providing the most helpful and trustworthy pregnancy and parenting information in the world. When creating and updating content, we rely on credible sources: respected health organizations, professional groups of doctors and other experts, and published studies in peer-reviewed journals. We believe you should always know the source of the information you're seeing. Learn more about our editorial and medical review policies.

Cleveland Clinic. 2020. Boy or girl – can you choose your baby's sex? a new window [Accessed November 2022]

CNN. 2019. Climate change will affect gender ratio among newborns, scientists say. a new window [Accessed November 2022]

Environment and Epidemiology. 2014. Climate change is associated with male:female ratios of fetal deaths and newborn infants in Japan. [Accessed November 2022]

Harvard Health Publishing. 2020. Fertility and diet: Is there a connection? a new window [Accessed November 2022]

Human Reproduction. 2018. Type of underwear worn and markers of testicular function among men attending a fertility center. a new window [Accessed November 2022]

Human Reproduction. 2012. Modifiable and non-modifiable risk factors for poor semen quality: a case-referent study. a new window [Accessed November 2022]

Journal of Epidemiology and Community Health. 2000. Declining male births with increasing geographical latitude in Europe. a new window [Accessed November 2022]

March of Dimes. 2020. Eating Healthy During Pregnancy. a new window [Accessed November 2022]

Mayo Clinic. 2021. Getting pregnant: How to get pregnant. a new window [Accessed November 2022]

Office on Women's Health. 2021. Ovulation calculator. a new window [Accessed November 2022]

Pediatrics International. 2013. Secular trends and latitude gradients in sex ratio at birth in Asia during the past 60 years. a new window [Accessed November 2022]

Proceedings of the Royal Society B. 2008. You are what your mother eats: evidence for maternal preconception diet influencing foetal sex in humans. a new window [Accessed November 2022]

Proceedings of the Royal Society B. 2008. Temperature-related birth sex ratio bias in historical Sami: warm years bring more sons. a new window [Accessed November 2022]

Reproductive Biomed Online. 2010. Female gender pre-selection by maternal diet in combination with timing of sexual intercourse--a prospective study. a new window [Accessed November 2022]

Kristen Sturt
Kristen Sturt is a freelance writer and editor specializing in health and wellness. She lives in New Jersey with her husband and their two boys. Her interests include cooking, vegetable gardening, travel, and Season 2, Episode 5 of Ted Lasso.