Guide
The Shettles method, explained
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The Shettles method is a natural approach to trying for a girl or a boy, proposed by Dr Landrum B. Shettles. It combines intercourse timing relative to ovulation with attention to the vaginal environment. The evidence is mixed and no outcome is guaranteed; Genesyx helps you follow the method consistently.
Where the theory comes from
Dr Landrum B. Shettles was an American physician and fertility researcher. In the 1960s he proposed that sperm carrying an X chromosome (which leads to a girl) and sperm carrying a Y chromosome (which leads to a boy) behave differently. His ideas were popularised in the book How to Choose the Sex of Your Baby, first published in 1970.
What the method proposes
| Trying for a girl (XX) | Trying for a boy (XY) | |
|---|---|---|
| Timing | Intercourse 2–4 days before ovulation | Intercourse as close to ovulation as possible |
| Vaginal environment | Theory suggests a more acidic environment | Theory suggests a more alkaline environment |
| Rationale in the theory | X-bearing sperm are said to survive longer | Y-bearing sperm are said to swim faster |
What the evidence says
Later studies have not consistently supported the theory. A widely cited 1995 study in the New England Journal of Medicine found no link between the timing of intercourse relative to ovulation and the sex of the baby. You can read more on our evidence page.
How Genesyx helps you follow it
The hardest part of the method is doing it consistently: tracking ovulation, checking your vaginal pH and following the right nutrition guidance, month after month. Genesyx brings those parts into one 90-day programme with a route-specific formula, a nutrition guide, at-home tests and a companion app.
A note on safety
Never douche or use home remedies to change your vaginal pH. They can disrupt healthy bacteria and cause infection. If you have any concerns, speak to your GP or a pharmacist.
Evidence for the Shettles theory is mixed. Genesyx helps you follow the theory consistently; no outcome is guaranteed. This page is general information, not medical advice.