Published on August 23rd, 2020 and Updated on April 1st, 2021
As you start on your journey to becoming a parent, you may dream of what your child will be like. Maybe you picture a softball champ who loves your mac and cheese recipes as much as she loves water colors. Or maybe you picture a dancer whose amazing natural rhythm only rivals his math skills. You may even keep your daydreams simple—a little boy, or a little girl.
With the variety of gender prediction tests available, is there also a way to improve the chances of having a boy or a girl?
Doctor, biologist, and reproduction scientist Dr. Landrum B. Shettles thought so.
Since 1960, couples have been trying to sway the odds for a baby girl or a boy using the Shettles Method. The Shettles Method essentially states that couples can determine the gender of their baby by creating the best environment for certain sperm—either sperm carrying an X chromosome (girl) or a Y chromosome (boy)—to thrive. But the science behind this practice is a bit more complicated than just putting out a welcome mat for preferred sperm.
Who is Landrum B. Shettles?
Dr. Landrum B. Shettles is the name behind this gender-determining method. He received both an MD and PhD in biology from Johns Hopkins University in the 1940s. From there, Shettles researched human reproductive physiology at Columbia University. He even contributed to the earliest work on in vitro fertilization. But Shettles is most known for his research on gender swaying—or determining the gender of a child before conception.
His work became The Shettles Method.
How is a Baby’s Gender Determined: A Crash Course
Understanding the basics of how a baby is made—on a cellular level, not a “birds and the bees” level—can help illuminate Shettles’ theory. First, let’s review some reproductive terminology:
- Sperm – Sperm is the male reproductive cell. It carries the father’s DNA and fertilizes the egg to create an embryo—the cluster of cells that become a baby.
- Egg – Not the kind you buy in a dozen. When it comes to human reproduction, an egg is the female reproductive cell. It holds the mother’s DNA and resides in the lining of the uterus.
- Embryo – Once the sperm fertilizes the egg, together, they make a whole greater than the sum of their parts—an embryo, the beginnings of a baby.
- Chromosome – Genetic information carried by both the egg and the sperm are called chromosomes. To create an embryo, the egg provides half of the chromosomes, while sperm the other.
As adults, we know that a baby’s gender isn’t determined by whatever the stork happens to pick up on your due date. Gender is determined at conception. So, what determines the gender of a baby?
When a man ejaculates, he releases between 40 million and 1.2 billion sperm. These sperm have to travel all the way through the vaginal canal, the cervix, and into the uterus to fertilize the egg. However, only about 100,000 of sperm make it into the uterus for a variety of reasons including:
- Having weirdly shaped “tails” that keep them from “swimming” well
- Missing essential structural parts that make male sperm cells unfit for the journey
- Some sperm go too far and land in a woman’s interstitial fluid, the fluid that surrounds her internal organs
And out of those 100,000, only one sperm can make it all the way home and into the egg to create an embryo. Once that one winning sperm has permeated the membrane of the egg, the egg creates an impenetrable external “shell” so extra male sperm cells can’t get in.
From there, the two cells (egg and sperm) each bring their own set of DNA to form the embryo—and the chromosomes in that DNA determines the gender of the baby.
The pair of chromosomes that determine gender are called sex chromosomes. These can be either X or Y chromosomes. Women have two X chromosomes while men have one X and one Y chromosome. To complete the pair, an egg provides one chromosome—an X chromosome—and the sperm provides the other—either an X or a Y chromosome.
Because the mom-to-be is the source of the egg’s genetic material, eggs can only provide an X chromosome. But since the dad-to-be has both X and Y chromosomes, sperm can bring either an X or a Y chromosome to the egg. That means if a sperm carrying an X chromosome fertilizes the egg, the embryo will wind up with two X chromosomes and will become a girl. If a Y-carrying sperm fertilizes the egg, the embryo will have one X and one Y chromosome and become a boy.
The Race to the Egg: Shettles’ Theory
In his pursuit to find a gender-determining method, Shettles researched everything he thought might affect the gender of a fetus, including the timing of sexual intercourse, sexual position, pH of bodily fluids—that is, the acidity of bodily fluids—and sperm. Based on his observations, Shettles believed that sperm carrying an X chromosome differed from sperm carrying a Y chromosome. He broke sperm down into two categories, Y-sperm and X-sperm.
- Y-Sperm – This sperm carries a Y chromosome and has the potential to create a boy. Shettles thought this particular sperm was faster, but had a shorter life span than X-sperm. He also believed that Y-sperm swim quicker in alkaline environments—or environments that weren’t very acidic—like the cervix and the uterus.
- X-Sperm – This sperm carries an X chromosome and has the potential to create a girl. In contrast with the Y-sperm, Shettles theorized that X-sperm are slower, but more resilient. The researcher also believed that X-sperm thrived in more acidic environments, like in the vaginal canal.
So for Shettles, the question became—how do couples create more accommodating environments for a specific kind of sperm?
The Shettles Method: Skewing the Results for a Girl or a Boy
All of Shettles’ studies of the human reproductive system led to his theory on how to create ideal environments for Y- or X-sperm. Shettles believed that ovulation, menstrual cycles, the female orgasm, and sexual position could all play a part in swaying the odds for a boy or a girl baby.
Shettles Method: How to Try for a Boy
According to Shettles’ observations, Y-sperm preferred alkaline—or not so acidic—environments. Here are his recommendations for giving Y-sperm their best shot at fertilization:
- Have sex on the day of woman’s ovulation day and up to 2-3 days later – Because a woman’s pH levels change based on her cycles, Shettles believed a woman was at her lowest acidity (and highest pH) just after ovulation.
- Try deeper penetration – Shettles believed that alkaline environments like the cervix and the uterus were ideal for Y-sperm. So the closer the ejaculate could get to those environments, the better. Shettles recommended couples who wanted a boy try sexual positions that allowed for the deepest possible penetration, specifically he advised entering the woman from behind.
- Let the mom-to-be orgasm first – Yup, Shettles even believed the female orgasm could affect the pH of the vagina. Because he thought that a woman’s natural post-orgasm secretions were more alkaline, he recommended women orgasm first to help create an alkaline environment for Y-sperm.
Shettles Method: How to Try for a Girl
Shettles believed X-sperm thrived in acidic environments. He theorized that adjusting the pH of a woman’s reproductive arena would help parents conceive a girl. The recommendations for increasing the chances of a X-sperm are pretty much the opposite of the Y-sperm:
- Save sex for after menstruation and stop before ovulation – To create a more acidic environment for X-sperm, Shettles recommended couples have sex right after a woman’s menstrual cycle—when he thought the vagina was at its most acidic—and stop sexual intercourse three days before ovulation.
- Try shallower penetration – According to Shettles, the high acidic environments of the vaginal canal were ideal for X-sperm. The idea was that X-sperm would speed on through the canal and into the womb while the Y-sperm, which preferred less acidic environments, would slow down or die off.
To do so, Shettles recommended couples try sexual positions that allowed for shallow penetration—like face-to-face or missionary—so the ejaculate deposit can be focused in the vaginal canal.
- Timing the female orgasm – Remember what Shettles believed about post-orgasm vaginal secretions? He thought that after a woman orgasmed, her vagina would naturally secrete alkaline fluids, which would increase her pH—making conditions less acidic and therefore less accommodating to X-sperm. He advised women to wait until their partner had ejaculated to orgasm.
Shettles Method Accuracy
While Shettles certainly was a pioneer in his day, the scientific accuracy of his method is a bit murky.
Although Shettles himself claimed his method has a 75% accuracy, independent researchers have disproved various aspects of Shettles accuracy and methodology several times over the past few decades. One research team even went so far as to disprove his claim on the different characteristics of X- and Y-sperm. On the other hand, several parenthood influencers and mommy-bloggers swear by the Shettles Method.
So really, it’s up to you if you want to try the Shettles Method. The good news? You can check Shettle’s accuracy for yourself with the SneakPeek Early Gender DNA Test!
Confirm Your Gender Swaying With the SneakPeek Gender Test
Whether you’re keeping your fingers crossed for a beautiful baby boy or a gorgeous baby girl, your parenting journey will be one full of discovery. And if you’re trying for one gender over the other, you may be counting down the days until you can find out whether your gender swaying methods worked.
Thanks to SneakPeek, you can find out your baby’s sex —and if your chosen gender-determining practices succeeded—as early as 8 weeks.
The SneakPeek Early Gender DNA test is a safe, easy-to-use, at-home gender blood test that lets you learn your baby’s gender in just a few days. And with a clinically-proven 99.9% accuracy rate, the SneakPeek Early Gender DNA test can help you feel confident about your soon-to-be son or daughter and what color to paint the nursery.
Learn more about your baby today with SneakPeek!
The New York Times. Dr. L.B. Shettles, 93, PIoneer in Human Fertility. https://www.nytimes.com/2003/02/16/nyregion/dr-l-b-shettles-93-pioneer-in-human-fertility.html
McGraw-Hill Medica. Medical Terminology in a Flash! Chapter 11: Reproductive System. https://fadavispt.mhmedical.com/content.aspx?bookid=2641§ionid=217178928
Healthline Parenthood. 12 Widely Believed Sperm Facts That Are Actually False. https://www.healthline.com/health/mens-health/sperm-myth-and-facts#8.-Every-sperm-is-healthy-and-viable
National Library of Medicine. Lack of significant morphological differences between human X and Y spermatozoa and their precursor cells (spermatids) exposed to different prehybridization treatments.
Psychology Today. Boy or Girl: Couples Trying to Load the Dice. https://www.psychologytoday.com/us/blog/how-we-do-it/201808/boy-or-girl-couples-trying-load-the-dice
Healthline Parenthood. Can you Choose the Sex of Your Baby? Understanding the Shettles Method. https://www.healthline.com/health/pregnancy/shettles-method
US National Library of Medicine. The molecular basis of fertilization. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5029953/