There is no natural method proven to reliably determine your baby’s sex. The only approach with near-certain results is IVF with genetic testing, which identifies embryo sex before transfer. That said, several popular timing and dietary strategies claim to shift the odds, and understanding what the science actually shows can help you decide what, if anything, is worth trying.
What Determines a Baby’s Sex
Every egg carries an X chromosome. Sperm carry either an X (which produces a girl) or a Y (which produces a boy). Whichever sperm fertilizes the egg decides the outcome. The entire basis of at-home sex selection methods rests on the idea that X-bearing and Y-bearing sperm behave differently, and that you can create conditions favoring one over the other.
Here’s the problem: modern research suggests those differences barely exist. A comprehensive review in Frontiers in Cell and Developmental Biology examined the evidence and found negligible or no differences between X and Y sperm in terms of shape, size, swimming speed, swimming pattern, strength, or response to acidic versus alkaline environments. The only confirmed difference is that X sperm carry about 2.8% more DNA. A study of over 58,000 human sperm cells found that exposing them to different pH levels for up to five days did nothing to change the ratio of X to Y sperm. This undercuts the core logic behind most natural methods.
The Shettles Method
The most widely known approach is the Shettles method, first published in the 1960s. It’s based on the theory that Y sperm are faster but more fragile, while X sperm are slower but longer-lived. To conceive a girl, Shettles recommended having intercourse two to three days before ovulation, then abstaining. The idea is that by the time the egg is released, the Y sperm have died off and the hardier X sperm remain. He also suggested avoiding female orgasm during conception (on the theory that orgasm creates a more alkaline environment favoring Y sperm) and using shallow penetration.
Shettles claimed a 75% success rate for couples trying for girls. Some early research appeared to support the timing component. A 1979 study of over 3,000 births published in The New England Journal of Medicine found that male babies were more often conceived when intercourse occurred closest to ovulation, which aligns with Shettles’ recommendations. But a 1991 study produced the opposite result, finding fewer male births when conception happened at ovulation. Then a 1995 New England Journal of Medicine study found no association at all between intercourse timing and baby sex.
The scientific evidence is genuinely contradictory, and the foundational claim that X and Y sperm differ in speed or resilience hasn’t held up to modern analysis. Despite this, Shettles’ book has remained in print for over 40 years, which speaks more to how badly people want a method than to how well this one works.
The Whelan Method
Elizabeth Whelan proposed a competing approach that also relies on intercourse timing but gives slightly different advice: have sex two to three days before ovulation for a girl. This happens to overlap with Shettles’ recommendation for daughters, though the two methods diverge on the reasoning and on their advice for conceiving boys. Neither has stronger scientific backing than the other, and both rest on the same unproven assumption that timing alone can meaningfully shift the odds.
Diet-Based Approaches
Some researchers have explored whether a mother’s mineral intake before conception influences baby sex. One study spanning 2001 to 2009 enrolled 175 women who wanted daughters and put them on a strict diet: low sodium, low potassium, high calcium, and high magnesium. Participants also took daily supplements of 400 to 600 mg of magnesium, 500 to 700 mg of calcium, and 5 to 7.5 micrograms of vitamin D.
The theory is that higher calcium and magnesium levels in the body may favor conditions for X sperm, while sodium and potassium may favor Y sperm. In practical terms, the diet emphasized dairy products, leafy greens, nuts, and beans while limiting processed foods, bananas, and salty snacks. Some small studies have reported modest shifts in sex ratios with this approach, but the evidence base is thin and the dietary restrictions are significant. No major medical organization endorses this as a reliable method.
IVF With Genetic Testing
If choosing your baby’s sex is genuinely important to you, IVF with preimplantation genetic testing (PGT) is the only method that offers near-100% accuracy. During a standard IVF cycle, eggs are fertilized in a lab, and the resulting embryos grow for several days. A few cells are then biopsied from each embryo and tested. The test reveals the chromosomal makeup, including whether the embryo is XX (female) or XY (male). You and your doctor then choose which embryo to transfer.
The process takes several weeks from start to finish. You’ll go through hormone injections to stimulate egg production, an egg retrieval procedure, a waiting period while embryos develop and testing results come back, and then the embryo transfer itself. The total cost in the United States typically falls between $20,000 and $27,000, though budget clinics may offer cycles starting around $11,000 to $12,000 and premium clinics can charge $30,000 to $35,000 or more. The genetic testing portion alone adds $2,000 to $5,000, depending on whether your clinic charges per embryo ($200 to $400 each) or a flat rate ($2,500 to $3,500).
Success isn’t guaranteed on the first cycle. Not every egg will fertilize, not every embryo will be viable, and not every transfer results in pregnancy. You may also end up with healthy embryos that are all the sex you didn’t want, which raises its own emotional and ethical questions. Still, when a female embryo is transferred, it is a female embryo. The sex identification itself is essentially certain.
Sperm Sorting Technology
A technology called MicroSort was developed to separate X-bearing sperm from Y-bearing sperm before insemination. The process uses a fluorescent dye that binds to DNA. Because X sperm contain slightly more genetic material, they glow a bit brighter under a laser, allowing a machine to sort them. In clinical trials, the sorted X-enriched samples averaged about 88% purity, and 92% of babies born from those samples were female.
MicroSort operated under an FDA investigational device exemption in the United States but never received full approval. It is not currently available in the U.S., though some international clinics offer similar flow cytometry sorting. The sorted sperm can be used with intrauterine insemination (a simpler, less expensive procedure than IVF) or combined with IVF for higher pregnancy rates. If you’re interested in this route, you’d need to research clinics abroad, primarily in Mexico and some other countries where the technology is offered.
Legal Restrictions on Sex Selection
Elective sex selection through IVF is legal in the United States, and a significant number of American fertility clinics offer it. But this is the exception globally. Most developed countries prohibit non-medical sex selection outright. Canada, the United Kingdom, France, Germany, Belgium, the Netherlands, Spain, Sweden, Switzerland, Australia, and Italy all ban or heavily restrict choosing your baby’s sex for personal preference. In these countries, genetic testing of embryos is permitted only when there’s a medical reason, such as screening for sex-linked genetic disorders like hemophilia or Duchenne muscular dystrophy.
If you live outside the United States, your options for guaranteed sex selection are limited to fertility tourism, traveling to a country where the procedure is legal. This adds significant cost and logistical complexity on top of an already demanding process.
Putting the Odds in Perspective
Without any intervention, the natural ratio of boys to girls at birth is close to 50/50, with a very slight skew toward boys (roughly 105 boys for every 100 girls). No natural method has been shown in rigorous studies to move those odds in a reliable, repeatable way. The timing methods, dietary changes, and positional advice you’ll find online are largely based on theories about sperm behavior that recent research has failed to confirm.
That doesn’t mean these methods can’t coincidentally “work” for individual couples. With a roughly 49% baseline chance of having a girl, many people who try any method will get the result they hoped for and credit the technique. But distinguishing a real effect from luck requires large, controlled studies, and those studies have not confirmed any natural approach.
For couples with a strong preference, IVF with genetic testing remains the only option backed by near-certain accuracy. For everyone else, the natural methods are low-risk to try (eating more calcium and magnesium, timing intercourse a few days before ovulation) but come with no guarantees beyond what chance already provides.