No natural method has been scientifically proven to reliably influence whether you conceive a girl. The only technique with near-certain accuracy is genetic testing of embryos during IVF, which correctly identifies sex about 99% of the time. That said, several popular methods claim to shift the odds in your favor, and they’re worth understanding so you can judge for yourself what’s plausible and what isn’t.
What Determines a Baby’s Sex
Every egg carries an X chromosome. Sperm carry either an X chromosome (which produces a girl) or a Y chromosome (which produces a boy). Whichever sperm fertilizes the egg decides the baby’s sex. The natural odds are close to 50/50, with a very slight lean toward boys: roughly 105 boys are born for every 100 girls worldwide.
Most natural sex-selection methods rest on the idea that X-bearing and Y-bearing sperm behave differently. Research has confirmed some physical differences: X-bearing sperm have slightly larger heads, longer tails, and greater overall surface area than Y-bearing sperm. But the practical significance of those differences is small, and scientists have not established that the two types swim at different speeds or survive for different lengths of time, which is the core assumption behind the most popular timing methods.
The Shettles Method
The Shettles method is the most widely known natural approach. Developed by Landrum Shettles in the 1960s, it’s based on the theory that Y-bearing sperm are faster but more fragile, while X-bearing sperm are slower but longer-lived. To conceive a girl, Shettles recommended having intercourse two to four days before ovulation, then abstaining as ovulation approaches. The idea is that by the time the egg is released, only the hardier X-bearing sperm would still be alive in the reproductive tract.
Shettles also recommended shallow penetration and avoiding female orgasm during intercourse, theorizing that both would create a more acidic environment near the cervix that favors X-bearing sperm. He claimed a 75% success rate for couples trying for a girl and 80% for those trying for a boy.
The scientific support is mixed at best. A 1979 study of over 3,000 births published in The New England Journal of Medicine did find that male babies were more often produced when intercourse occurred closest to ovulation, which aligns with Shettles’s framework. But a 1991 study in The American Journal of Obstetrics and Gynecology found the opposite: fewer boys when conception happened near ovulation. Then a 1995 New England Journal of Medicine study refuted the entire premise, finding no association between intercourse timing and fetal sex at all. Perhaps most damaging, a later study on sperm shape found no meaningful physical differences between X-bearing and Y-bearing sperm, undermining the biological foundation Shettles built his method on.
The Whelan Method
Elizabeth Whelan proposed a competing approach that actually contradicts Shettles on some points. For conceiving a girl, Whelan recommended having intercourse two to three days before ovulation, which overlaps with the Shettles advice, but she based her reasoning on different biological mechanisms related to hormonal conditions in the reproductive tract at various points in the cycle.
Whelan suggested tracking your basal body temperature to identify ovulation. The day before your temperature spikes is likely ovulation day. During the following cycle, you would time intercourse based on that pattern. Like the Shettles method, Whelan’s approach lacks strong scientific validation, and the fact that these two methods sometimes give contradictory advice highlights how uncertain the underlying science remains.
Maternal Diet and Mineral Intake
A separate line of research has explored whether what you eat before conception influences fetal sex. The theory focuses on four minerals: calcium, magnesium, sodium, and potassium. Retrospective diet surveys found that mothers who had predominantly female children tended to eat diets high in calcium and magnesium, while mothers of mostly male children consumed more sodium and potassium. A 2008 British dietary survey of 740 women confirmed a similar pattern, with higher sodium and potassium intake linked to bearing boys.
Based on this, some researchers have studied whether a preconception diet low in sodium and potassium but high in calcium and magnesium, combined with intercourse timed well before ovulation, could improve the chances of conceiving a girl. The results have shown some promise, but the studies are small, and it’s difficult to separate the effect of diet from the effect of timing or simple chance. No major medical organization recommends dietary changes as a reliable sex-selection strategy.
If you wanted to try this approach anyway, it would mean emphasizing dairy products, leafy greens, nuts, and seeds (rich in calcium and magnesium) while reducing salty and processed foods. Any significant dietary changes during the preconception period are worth discussing with a healthcare provider to make sure your overall nutrition stays adequate.
IVF With Genetic Testing
The only method that can select a baby’s sex with near certainty is IVF combined with preimplantation genetic testing. During a standard IVF cycle, eggs are fertilized in a lab and allowed to develop into embryos. Before transfer, a few cells are biopsied from each embryo and tested. This reveals the chromosomal makeup, including whether the embryo is XX (female) or XY (male), with about 99% accuracy.
The total cost typically falls between $25,000 and $27,000, with the genetic testing portion alone running $2,000 to $5,000. It’s important to understand that selecting an embryo of the desired sex doesn’t guarantee a live birth. Success rates per transfer depend heavily on age: women under 35 have a 50 to 60% live birth rate per transfer, dropping to 40 to 45% for ages 35 to 37, 30 to 35% for ages 38 to 40, and under 20% for women over 41.
Sex selection through IVF is legal in the United States but restricted or banned in many other countries, including the UK, Canada, Australia, and much of Europe, where it’s only permitted for medical reasons such as avoiding sex-linked genetic disorders.
Putting the Odds in Perspective
With a natural 50/50 baseline, any method that doesn’t involve directly identifying embryos is working with very thin margins. Even if a timing or diet method shifted your odds from 50% to, say, 55%, you’d need a very large number of pregnancies to notice the difference. This is part of why studies keep producing contradictory results: the effect, if it exists at all, is small enough that it’s easily drowned out by normal statistical variation.
Couples who try a natural method and conceive a girl often credit the method, while those who conceive a boy tend not to report their experience. This reporting bias inflated the success rates in Shettles’s original claims and continues to shape anecdotal evidence online. The honest picture is that natural methods are unproven, dietary approaches are suggestive but far from conclusive, and IVF with genetic testing is the only option backed by hard data.