Can You Really Choose Baby Gender? What Science Says

The desire to choose baby gender is as old as civilization itself. From ancient folklore to modern reproductive technology, parents have always looked for ways to influence whether they have a boy or a girl. Today, the only method with near-certain accuracy is preimplantation genetic testing (PGT) during IVF, which can identify the sex of embryos with over 99% accuracy. Natural methods like diet, timing of intercourse, and stress reduction remain popular but are not supported by strong scientific evidence. If you are curious about what works and what does not, this guide ranks six common approaches to help you choose baby gender based on the actual science behind each.

The natural probability of having a boy versus a girl in the United States is close to 50/50, with a slight natural skew toward boys at about 105 males for every 100 females at birth.

Method 1: IVF with Preimplantation Genetic Testing (PGT)

The only scientifically proven way to choose baby gender with near-total certainty is through in vitro fertilization combined with preimplantation genetic testing. During IVF, eggs are fertilized in a laboratory and the resulting embryos develop for five to six days. A small biopsy of cells is then taken from each embryo and analyzed for chromosomal composition. Since girls carry XX chromosomes and boys carry XY, the test reveals the sex of each embryo before transfer.

PGT identifies embryo sex with an accuracy rate exceeding 99%. In the United States, sex selection through PGT is legal, although the ASRM Ethics Committee stated in 2022 that while using PGT to prevent sex-linked genetic diseases is ethically acceptable, using it purely for nonmedical sex selection remains ethically controversial and should not be encouraged. Many other countries, including the UK, Canada, China, India, and most of Europe, prohibit sex selection for nonmedical reasons entirely.

A single IVF cycle with PGT costs between $15,000 and $25,000 in the US, making it the most expensive way to choose baby gender. It is also the most medically invasive, requiring hormone injections, egg retrieval surgery, and embryo transfer. For couples already undergoing IVF for fertility reasons, PGT may be offered as part of the process, and sex information becomes available as a byproduct of the genetic screening.

Method 2: The Shettles Method (Timing of Intercourse)

The Shettles method, developed by Dr. Landrum Shettles in the 1960s, is one of the most widely known natural approaches to choose baby gender. The theory is based on the idea that male sperm (carrying a Y chromosome) swim faster but have shorter lifespans, while female sperm (X chromosome) are slower but live longer.

According to this method, to conceive a boy, you should have intercourse as close to ovulation as possible, giving the faster Y sperm the best chance of reaching the egg first. To conceive a girl, you should have sex two to four days before ovulation, so that by the time the egg is released, only the hardier X sperm remain alive.

While the underlying biology about sperm speed and lifespan has some basis in laboratory observations, clinical studies have not consistently confirmed that the Shettles method actually works. A review published in the Annual Review of Genomics and Human Genetics notes that natural timing-based methods have not been validated by rigorous trials. Scientific opinion on whether timing of conception can reliably influence sex remains divided. There is no harm in trying, but you should not expect guaranteed results.

Method 3: Diet and Nutrition

Numerous theories claim that what you eat before and during conception can help you choose baby gender. Some of the most commonly cited include eating more calories, having cereal for breakfast, and following a potassium-rich diet to increase your chances of having a boy. For a girl, some believe that a diet high in calcium and magnesium may shift the odds.

A 2008 study from the University of Exeter found a statistical association between women who consumed more calories around the time of conception and a slightly higher likelihood of having a boy. However, the effect was small and has not been consistently replicated in other studies. No major reproductive health organization recommends dietary changes as a reliable way to choose baby gender.

When trying to conceive, the most important dietary goal is to maintain a balanced, nutrient-rich diet that supports your overall health and gives your future baby the best start. Eating well is always a good idea, but counting on specific foods to determine your baby’s sex is not supported by firm evidence.

Method 4: Stress Levels and Environment

A 2011 study examining pregnant women exposed to a major earthquake in Chile found that women under extreme stress were less likely to give birth to boys. Researchers theorized that male embryos (XY) may be more vulnerable to high-stress environments, or that stress hormones may create conditions more favorable to female sperm (X).

While this is an interesting finding, it applies to extreme stress conditions and is not a practical or healthy method to choose baby gender. High stress levels can make conception harder overall, and deliberately increasing stress would be harmful to both your health and your baby’s. Instead, focus on reducing stress through meditation, yoga, exercise, and adequate sleep, all of which support better fertility outcomes regardless of the baby’s sex.

Method 5: IVF Embryo Transfer Timing

According to a study from the University of New South Wales in Australia, the timing of embryo transfer during IVF may influence the likelihood of having a boy or a girl. Women who had their embryo transferred four to five days after fertilization (blastocyst transfer) had a 56% chance of having a boy, compared to 49% for those whose embryo was transferred at day two or three.

Researchers believe this difference may be related to how male and female embryos develop at different rates in laboratory conditions. Male embryos tend to develop slightly faster, which could give them an advantage in day-five transfers. However, this is not a method you can use to actively choose baby gender, as the transfer timing is determined by your fertility specialist based on medical factors, not sex preference.

Method 6: Genetic Predisposition

Many people try to predict or influence their baby’s sex based on family patterns. If a family has mostly boys, the assumption is that the next baby will also be a boy. While this is a common belief, no published research has conclusively demonstrated a genetic predisposition for producing one sex over the other. The sex of each baby is determined independently by which sperm (X or Y) fertilizes the egg, and this remains essentially random with each conception.

What About Using a Sperm Donor to Choose Baby Gender?

If you are using a sperm donor to conceive, the same principles apply. Natural methods like timing and diet have no proven reliability. The only certain way to choose baby gender when using donor sperm is through IVF with PGT. Some sperm banks offer sperm sorting technologies that claim to separate X and Y sperm before insemination, but these methods are not widely available in the US and their accuracy is limited compared to PGT.

On CoParents.com, a co-parenting and sperm donation platform active since 2008 with over 150,000 users, many intended parents connect with known donors to start their families. While the platform helps you find the right donor based on health history, values, and desired level of involvement, the sex of the baby will ultimately depend on which sperm fertilizes the egg, unless you pursue IVF with genetic testing.

The Bottom Line on Trying to Choose Baby Gender

If you want to try natural methods to influence your baby’s sex, there is no harm in adjusting the timing of intercourse or maintaining a specific diet, as long as you stay healthy and do not develop unrealistic expectations. These methods are unproven but harmless. If having a child of a specific sex is medically important, for example to avoid sex-linked genetic disorders like hemophilia or Duchenne muscular dystrophy, IVF with PGT is the only reliable option.

For everyone else, the healthiest approach is to focus on having a healthy baby, regardless of sex. Eat well, manage stress, track your ovulation accurately, and work with your doctor to optimize your fertility. Whether you end up with a boy or a girl, the real gift is a healthy child.

FAQ

Can you really choose baby gender naturally?

No natural method has been scientifically proven to reliably determine a baby’s sex. The Shettles method, dietary changes, and other folk approaches may slightly shift probabilities according to some studies, but the effects are small and inconsistent. The only proven way to choose baby gender is through IVF with preimplantation genetic testing.

How accurate is IVF with PGT for sex selection?

PGT identifies embryo sex with an accuracy rate exceeding 99%. It is the only method that can guarantee a specific sex before pregnancy begins. However, it requires a full IVF cycle and costs $15,000 to $25,000 in the United States.

Is sex selection legal in the US?

Yes. The United States is one of the few countries where sex selection through IVF with PGT is legal for both medical and nonmedical reasons. However, the ASRM Ethics Committee has stated that nonmedical sex selection should not be encouraged and raises ethical concerns about gender bias. Many other countries prohibit nonmedical sex selection entirely.

Does eating certain foods help you choose baby gender?

Some studies have found weak associations between higher calorie intake and a slightly increased likelihood of having a boy, or between calcium-rich diets and having a girl. However, these findings are not strong enough to constitute a reliable method. Maintaining a balanced diet is far more important for your health and your baby’s development than trying to influence sex through nutrition.

Can stress affect whether you have a boy or a girl?

Research suggests that extreme stress may slightly reduce the likelihood of having a boy, possibly because male embryos are more vulnerable to stressful conditions. However, this is not a practical or healthy strategy to choose baby gender. Reducing stress supports better fertility and pregnancy outcomes regardless of the baby’s sex.