For generations, parents-to-be have wondered: Is there anything we can do to influence whether we have a boy or a girl? While modern medicine offers high-tech options like preimplantation genetic testing (PGT) during IVF, many couples are curious about natural methods—and the most well-known is the Shettles Method.
Developed in the 1960s by Dr. Landrum B. Shettles, a pioneer in in-vitro fertilization research, this method proposes that the timing of intercourse relative to ovulation can tip the odds toward conceiving either a boy or a girl. Dr. Shettles outlined his theory in the bestselling book "How to Choose the Sex of Your Baby", which has sold over a million copies worldwide.
But here's the crucial context: while the Shettles Method has passionate advocates and has been practiced for decades, independent scientific research has not consistently validated its effectiveness. We'll explore both the theory and the evidence, so you can make an informed decision about whether to try it.
The Theory: X-Sperm vs Y-Sperm
The Shettles Method is based on observed differences between the two types of sperm that determine a baby's biological sex:
How Sex Is Determined
Every egg carries an X chromosome. Sperm carry either an X chromosome (female) or a Y chromosome (male). If an X-sperm fertilizes the egg, the result is XX = Girl. If a Y-sperm fertilizes the egg, the result is XY = Boy.
Dr. Shettles proposed that X-bearing and Y-bearing sperm have distinct physical and behavioral characteristics that can be exploited through strategic timing:
Y-Sperm (Boy)
Carries the male chromosome
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Smaller & Lighter
Less genetic material to carry (Y is smaller than X chromosome)
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Faster Swimmers
Can reach the egg more quickly due to size advantage
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More Fragile
Die off more quickly, less tolerant of acidic environment
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Shorter Lifespan
Survive approximately 24-48 hours in reproductive tract
"Sprint runners" — fast but tire quickly
X-Sperm (Girl)
Carries the female chromosome
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Larger & Heavier
More genetic material (X is larger than Y chromosome)
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Slower Swimmers
Move more methodically toward the egg
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More Resilient
Better able to withstand acidic vaginal environment
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Longer Lifespan
Can survive 3-5 days in the reproductive tract
"Marathon runners" — slower but more endurance
| Characteristic | Y-Sperm (Boy) 👦 | X-Sperm (Girl) 👧 |
|---|---|---|
| Size | Smaller | Larger |
| Swimming Speed | Faster | Slower |
| Lifespan | 24-48 hours | 3-5 days |
| pH Tolerance | Prefers alkaline | Tolerates acidic |
| Overall | Fast but fragile | Slow but sturdy |
Based on these proposed differences, Dr. Shettles developed timing strategies designed to give either Y-sperm or X-sperm an advantage in the race to fertilize the egg.
👦 Strategy for Conceiving a Boy
Since Y-sperm are theorized to be faster but less resilient, the Shettles Method recommends timing intercourse as close to ovulation as possible. The logic is:
The "Boy" Timing Strategy
Have Intercourse on Ovulation Day (or 12 hours before)
When the egg is already released or about to be released, the faster Y-sperm have a shorter distance to travel and can reach the egg before the X-sperm.
Abstain for 4-5 Days Before the Fertile Window
This allows sperm count to build up, maximizing the number of faster Y-sperm in the ejaculate.
Use Deeper Penetration Positions
Depositing sperm closer to the cervix (near the more alkaline cervical mucus) gives Y-sperm a shorter, more favorable journey.
Female Orgasm Before or During Male Ejaculation
Shettles theorized that female orgasm produces secretions that make the vaginal environment more alkaline, favoring Y-sperm survival.
Visual Timing Guide for a Boy
Goal: Have intercourse as close to ovulation as possible (day of or 12 hours before)
💡 Key Insight: The success of this timing depends on accurately knowing when you ovulate. Combine ovulation predictor kits (OPKs) with our fertility calculator to pinpoint your ovulation day.
👧 Strategy for Conceiving a Girl
Since X-sperm are theorized to be slower but more resilient, the Shettles Method recommends timing intercourse 2-4 days before ovulation, then abstaining until after ovulation passes. The logic is:
The "Girl" Timing Strategy
Have Intercourse 2-4 Days Before Ovulation
By the time the egg is released, the faster but fragile Y-sperm will have died off, leaving the hardier X-sperm still waiting.
Abstain Starting 1-2 Days Before Ovulation
Stop intercourse before ovulation to ensure no "fresh" Y-sperm are present when the egg is released.
Use Shallower Penetration Positions
Depositing sperm further from the cervix (in the more acidic vaginal environment) may disadvantage the more fragile Y-sperm.
Avoid Female Orgasm
According to Shettles, avoiding orgasm keeps the vaginal environment more acidic, which may disadvantage Y-sperm.
Visual Timing Guide for a Girl
Goal: Have intercourse 2-4 days before ovulation, then abstain until after
⚠️ Important Trade-off: The "girl" strategy involves stopping intercourse before peak fertility, which may reduce your overall chances of conception that cycle. If getting pregnant quickly is your priority over gender preference, this timing may not be ideal.
Quick Comparison: Boy vs Girl Timing
| Factor | For a Boy 👦 | For a Girl 👧 |
|---|---|---|
| Timing | Day of ovulation (or 12hrs before) | 2-4 days before ovulation |
| Abstinence | 4-5 days before fertile window | From 1-2 days before ovulation onward |
| Position | Deeper penetration | Shallower penetration |
| Female Orgasm | Encouraged (before/during) | Avoided |
| Environment | More alkaline (favors Y) | More acidic (favors X) |
Additional Shettles Recommendations
Beyond timing, Dr. Shettles suggested several additional factors that might influence gender selection:
☕ Caffeine (for Boys)
Shettles suggested the male partner drink a caffeinated beverage 15-30 minutes before intercourse to potentially make Y-sperm more active. No scientific evidence supports this.
🩲 Temperature (for Boys)
The male partner should wear loose underwear and avoid hot baths before conception to keep sperm counts higher. General fertility advice, not gender-specific.
🧴 Douching (Controversial)
Shettles originally suggested douching with baking soda (for boys) or vinegar (for girls) to alter pH. Medical professionals strongly advise against vaginal douching as it disrupts natural flora and increases infection risk.
🍎 Diet Theories
Some claim that certain diets (high sodium/potassium for boys, high calcium/magnesium for girls) can influence gender. No reliable scientific evidence supports dietary gender selection.
What Does Science Actually Say?
This is where we need to be completely transparent: the scientific evidence for the Shettles Method is weak and contradictory.
🔬 What Research Shows
- ✗ The sperm size/speed theory is disputed: Modern research using computer-assisted sperm analysis (CASA) has not consistently found significant speed differences between X and Y-bearing sperm.
- ✗ Multiple studies found no effect: A 1995 study in the New England Journal of Medicine found no relationship between timing of intercourse and baby's sex. Similar results were found in other large studies.
- ✗ One study suggested the opposite: A 2001 study actually found that intercourse close to ovulation was associated with slightly more girls, contradicting Shettles' theory.
- ? No professional endorsement: The American College of Obstetricians and Gynecologists (ACOG) and other medical organizations do not endorse any timing-based gender selection method.
📊 The Real Odds
The natural sex ratio at birth is approximately 105 boys to 100 girls (about 51% boys, 49% girls). This ratio remains remarkably consistent regardless of timing, position, or other natural methods. The only proven methods for gender selection are:
- PGT (Preimplantation Genetic Testing) during IVF — 99%+ accurate
- Sperm sorting (MicroSort) — 70-90% effective (limited availability)
⚠️ Important Disclaimer: This Method Is Not Scientifically Proven
The Shettles Method is a theory, not a medically validated technique. While Dr. Shettles claimed success rates of 75-90%, independent scientific studies have not consistently replicated these results.
The natural odds of conceiving either a boy or girl remain approximately 50/50 regardless of timing, position, or other natural methods.
If you choose to try this method, do so with realistic expectations. Do not be disappointed if the outcome differs from your preference—every healthy baby is a blessing.
This information is for educational purposes only. Consult with a healthcare provider for medical advice about conception and family planning.
Should You Try the Shettles Method?
Ultimately, whether to try the Shettles Method is a personal decision. Here's our balanced take:
Reasons You Might Try It
- • It's free and natural with no medical intervention
- • No known health risks (aside from douching, which you shouldn't do)
- • It doesn't hurt to try if you're already tracking ovulation
- • Some couples find it fun and engaging
- • Even if it's placebo, the emotional benefit may be real
Reasons to Be Cautious
- • No reliable scientific evidence it works
- • The "girl" timing may reduce conception chances per cycle
- • May lead to disappointment if results differ
- • Could create emotional strain in your relationship
- • Risk of unhealthy attachment to a specific gender
If you do decide to try the Shettles Method, we encourage you to:
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Keep expectations realistic — remember the odds are essentially 50/50
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Don't sacrifice conception chances — if pregnancy is the priority, don't skip peak fertility days
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Prepare emotionally — be ready to embrace whichever gender you're blessed with
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Avoid harmful practices — never douche, which can cause infections and disrupt fertility
At the end of the day, the most important outcome is a healthy pregnancy and a healthy baby—regardless of gender. Every child is a unique gift, and the love you'll feel for your baby will transcend any preference you had beforehand.
Ready to Find Your Ovulation Day?
Whether or not you try the Shettles Method, knowing your ovulation date is essential for conception. Use our Smart Fertility Calculator to identify your fertile window.
Calculate My Fertile DaysReferences & Further Reading
- • Shettles, L.B., & Rorvik, D.M. (2006). How to Choose the Sex of Your Baby. Broadway Books.
- • Wilcox, A.J., et al. (1995). Timing of sexual intercourse in relation to ovulation. New England Journal of Medicine, 333(23), 1517-1521.
- • Gray, R.H., et al. (1998). Sex ratio associated with timing of insemination and length of the follicular phase. Human Reproduction, 13(5), 1397-1400.
- • American College of Obstetricians and Gynecologists (ACOG). FAQ: Infertility.