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The Shettles Method: Can You Really Choose the Sex of Your Baby?
Can you actually influence whether you conceive a boy or a girl?
This is one of those fertility topics that is fascinating, controversial, and honestly, just fun to talk about.
While we were preparing to conceive, I came across How to Choose the Sex of Your Baby by Dr. Landrum Shettles. I listened to the book mostly out of curiosity, but it ended up tying into so much of what I already teach about fertility awareness, cervical mucus, ovulation, timing intercourse, and understanding the fertile window.
Before we get into it, an important disclaimer:
The Shettles Method is a theory. It is not a scientifically proven or guaranteed way to choose the sex of your baby.
The sex of a baby is ultimately determined by whether an X-bearing or Y-bearing sperm fertilizes the egg, and there is still a significant element of chance involved.
That said, the theory is an interesting way to explore reproductive physiology and, perhaps most importantly, it gives us an excuse to talk about something I believe is incredibly valuable: understanding your cycle.
What Is the Shettles Method?
Dr. Landrum Shettles was a physician and fertility researcher who developed a theory of natural sex selection based largely on proposed differences between X-bearing and Y-bearing sperm.
An egg contributes an X chromosome.
The sperm contributes either:
- An X chromosome, resulting in an XX embryo
- A Y chromosome, resulting in an XY embryo
The Shettles theory proposed that X-bearing and Y-bearing sperm behaved differently.
According to the theory, Y-bearing sperm were believed to be:
- Faster
- Smaller and lighter
- Shorter lived
- More sensitive to acidic environments
X-bearing sperm were proposed to be:
- Slower
- Larger
- More resilient
- Longer lived
- Better able to tolerate an acidic environment
From these proposed differences came the idea that the timing of intercourse in relation to ovulation could potentially favour one group of sperm over the other.
Again, these proposed differences have not been consistently supported by modern research, so think of this as an interesting historical fertility theory rather than a reliable sex-selection technique.
The Shettles Method for Conceiving a Boy
According to the Shettles theory, couples hoping to conceive a boy should have intercourse as close to ovulation as possible.
The reasoning was simple.
If Y-bearing sperm were faster but less resilient, having sperm arrive around the same time the egg is released could theoretically give the faster sperm an advantage.
Shettles therefore recommended intercourse:
On the day of ovulation or very close to ovulation.
The theory also included other recommendations such as deeper penetration and female orgasm, based on the idea that these factors might create an environment that was more favourable to Y-bearing sperm.
Some versions of the method even suggested altering vaginal pH.
That is one recommendation I would personally not follow.
The vaginal microbiome and its naturally acidic environment play an important role in protecting against infection. I would not recommend douching or intentionally manipulating vaginal pH in an attempt to influence the sex of a baby.
The Shettles Method for Conceiving a Girl
For couples hoping to conceive a girl, the theory essentially reverses the timing.
Shettles recommended intercourse approximately:
Two to three days before ovulation, followed by abstinence until ovulation had passed.
The proposed idea was that faster, shorter-lived Y-bearing sperm might arrive first but die before the egg was released, while the supposedly more resilient X-bearing sperm could remain viable long enough to fertilize the egg.
The method also recommended shallower penetration and avoiding female orgasm, again based on theories surrounding vaginal pH and sperm survival.
Whether those recommendations meaningfully influence the sex of a baby is another question entirely.
But the timing conversation brings us to something far more useful.
To Use Any Timing Method, You Need to Understand Ovulation
This is where the Shettles Method becomes genuinely interesting from a fertility education perspective.
Whether you care about conceiving a boy, conceiving a girl, or simply conceiving at all, you need to understand when your fertile window opens and closes.
And your body gives you clues.
Cervical Mucus
One of the most valuable fertility signs is cervical mucus.
As estrogen rises approaching ovulation, cervical mucus changes.
You may notice mucus that becomes:
- Wetter
- Clearer
- More slippery
- More stretchy
- Similar to raw egg white
This highly fertile cervical mucus helps sperm survive and move through the reproductive tract.
You may also experience non-peak mucus, which might appear more creamy, lotion-like, white, or pasty.
An important point is that pregnancy can still occur when intercourse happens on days with non-peak cervical mucus. The appearance of cervical mucus tells us that the fertile window may be opening.
Cervical mucus does far more than simply tell us ovulation is approaching. It helps create an environment where sperm can survive, travel, and potentially reach the egg.
Basal Body Temperature
Basal body temperature, or BBT, is another tool commonly used in fertility awareness.
You take your temperature first thing in the morning, ideally before getting out of bed.
After ovulation, progesterone rises and produces a small increase in body temperature.
A sustained temperature shift can therefore help us confirm that ovulation has likely already occurred.
This distinction matters.
BBT is much better at confirming ovulation retrospectively than predicting the exact moment it will occur.
If you're trying to conceive, cervical mucus gives you more useful real-time information about when your fertile window is opening.
Ovulation Predictor Kits
Ovulation predictor kits, or OPKs, measure luteinizing hormone in the urine.
LH normally surges before ovulation, so a positive test can tell you that ovulation may be approaching.
But an LH surge does not absolutely guarantee that ovulation occurred.
This can be especially important for people who experience irregular cycles or conditions such as PCOS, where LH patterns can sometimes make interpretation more complicated.
This is why I prefer looking at multiple fertility signs rather than relying on a single test.
Cervical mucus.
Basal body temperature.
Cycle patterns.
And, when appropriate, LH testing.
Together, they give us a much clearer picture.
What Actually Happens After Intercourse?
This is the part of reproductive physiology that I find fascinating.
When sperm enter the reproductive tract during the fertile window, they still have an enormous journey ahead of them.
They have to:
- Survive the vaginal environment.
- Travel through cervical mucus.
- Pass through the cervix and uterus.
- Enter the correct fallopian tube.
- Remain viable until an egg is available.
- Successfully fertilize that egg.
Meanwhile, after ovulation, the egg is captured by the fimbriae near the end of the fallopian tube.
Fertilization typically occurs in the fallopian tube.
Once one sperm successfully penetrates and fertilizes the egg, the egg undergoes changes that prevent additional sperm from entering.
So while we sometimes simplify conception as “sperm meets egg,” there is an incredible amount of biology happening behind the scenes.
Can Sperm Really Survive for Five Days?
Under favourable conditions, sperm can survive in the female reproductive tract for several days.
This is exactly why pregnancy can occur from intercourse that happened before ovulation.
If fertile cervical mucus is present, sperm may remain viable while waiting for an egg to be released.
The egg itself has a much shorter fertile lifespan after ovulation.
This is why, from a fertility perspective, intercourse in the days leading up to ovulation is so important.
You do not necessarily want to wait until you think ovulation has already happened.
So, Does the Shettles Method Actually Work?
This is where we have to separate an interesting theory from strong scientific evidence.
Shettles reported high success rates for couples following his method.
However, later research has not consistently supported the idea that intercourse timing can reliably determine the sex of a baby.
That means I would never tell someone that following these timing rules will give them a boy or a girl.
There is still a large element of chance.
And if having a baby of one particular sex feels emotionally essential to you, a natural timing method should absolutely not be treated as a guarantee.
What I Actually Like About the Shettles Method
Interestingly, my favourite part of this entire theory has almost nothing to do with choosing a baby's sex.
It encourages body literacy.
To even attempt the method, you need to understand:
- Your cervical mucus
- Your fertile window
- Your typical cycle length
- When ovulation may be approaching
- How to confirm ovulation afterwards
- How sperm and egg survival affect conception
Those are incredibly useful things to know regardless of whether you care about having a boy or a girl.
I often recommend tracking several cycles before actively trying to conceive.
Not because every cycle will be identical.
They won't.
But tracking gives you a baseline.
You start learning:
“When does my cervical mucus usually appear?”
“What does fertile mucus look like for me?”
“When do I typically see my temperature shift?”
“How long is my luteal phase?”
That information can transform conception from something mysterious into something you understand and participate in.
Our Own Little Experiment
When my husband and I were preparing to conceive, we talked about the Shettles theory too.
Would we be thrilled with a boy?
Absolutely.
Would we be thrilled with a girl?
Absolutely.
A baby is a baby, and our biggest goal was a healthy pregnancy and healthy baby.
But we decided it would be fun to experiment with one part of the Shettles theory: timing intercourse close to ovulation.
No pH manipulation.
No elaborate rules.
Just fertility awareness, knowing my cycle well, identifying my fertile window, and trying to time intercourse as close to ovulation as we could.
And, in our case, we tried for a boy... and we got our little boy, Harlan.
Did the Shettles Method cause that?
We will never know.
It could very easily have been chance, and our experience certainly does not prove that the method works.
But it made the conception process fun, intentional, and gave us one more reason to appreciate how valuable it is to understand the menstrual cycle.
For me, that is still the biggest takeaway.
Want to Understand Your Fertility More Deeply?
If reading this has you thinking, I have no idea when I actually ovulate, that is exactly the kind of work I love doing with women.
My fertility packages go far beyond simply predicting ovulation.
We look at your cycle as a whole, including your fertile window, cervical mucus patterns, ovulation, nutrition, lifestyle, exercise, and the factors that can support both egg and sperm health before conception.
The goal is not to obsess over making everything perfect.
It is to help you understand your body, identify areas that may need support, and enter conception feeling informed and intentional.
If you are preparing to conceive and would like personalized support, you can learn more about my fertility nutrition and cycle coaching packages through my website.
Whether you are several months away from trying, actively TTC, or simply want to understand your cycle better, there is so much useful information we can gather before pregnancy even begins.
The Bottom Line
The Shettles Method remains one of the best-known theories for naturally influencing the sex of a baby.
Is it interesting?
Absolutely.
Is it guaranteed?
Definitely not.
In our case, we tried timing intercourse for a boy and ended up welcoming our son, Harlan. That makes for a pretty fun story, but it is still just one story.
What I take much more seriously is the fertility awareness behind it.
Learning when you're fertile, understanding cervical mucus, recognizing ovulation patterns, and becoming more connected to your menstrual cycle are powerful skills whether you are hoping for a boy, a girl, or simply a healthy pregnancy.
So if you want to experiment with the Shettles Method for fun, understand what it is:
A theory, not a promise.
Then take the part that I think matters most.
Learn your body.
Learn your cycle.
Nourish yourself deeply.
And prepare intentionally for the family you're hoping to build.
This article is for educational purposes only and is not intended to diagnose, treat, or provide individualized medical advice. Speak with your healthcare provider regarding your individual fertility and reproductive health needs.