Can Sex Position Determine a Baby's Gender?

Can the position in which you have sex influence your baby's sex? Learn what science says about various at-home methods of sex selection.

People have been trying to figure out ways to influence the sex of babies for centuries, but when it comes to baby-making, "there are really no lovemaking positions that can influence the gender of your baby," says Jeffrey Steinberg, M.D., director of the gender selection program at the Fertility Institutes in Los Angeles. That is to say that the position in which you have sex won't influence whether you conceive a boy or girl.

For better or worse, most of us are still at the whim of Mother Nature when it comes to the sex of our babies, despite the interesting folklore surrounding sex selection. Think: "Eat meat and salty food to get a boy; splurge on desserts to get a girl." Or "make love standing up or when there's a quarter moon if you want a male, but stick to the missionary position and make love during a full moon for a female."

You can also check out a 700-year-old Chinese conception chart that tells people which dates will result in male or female conceptions based on the gestational parent's age and the month of conception. But there's no scientific evidence that any of this works.

In one study published in the American Journal of Obstetrics & Gynecology, researchers in Massachusetts looked at the delivery records of babies born between 1995 and 2008 to see if the claim of 93% to 99% accuracy for these charts held up. But what they found was that you'd have the same odds from a coin toss in correctly guessing the sex of your baby.

Nonetheless, sex selection is big business. You may have noticed sex selection kits marketed online that guarantee results with douches, vitamins, or do-it-yourself artificial insemination kits. Not one of them has been sanctioned by science.

The best-known book on sex prediction is by in vitro fertilization pioneer Landrum Shettles, M.D., who first published a report in the 1960s on the distinctive characteristics of X-bearing (female-producing) and Y-bearing (male-producing) sperm and compiled a series of noninvasive, low-tech family planning techniques.

For instance, the late Dr. Shettles advised couples seeking a male to have sex as close to ovulation as possible because that's when vaginal and cervical fluids tend to be the most alkaline, a condition that makes conception most favorable for the less-hearty Y sperm. However, further studies have shown that Dr. Shettles' theory is likely as effective as that coin toss.

In 2016, researchers found no link between the style and timing of intercourse and the sex of the conceived fetus. And in 2020, researchers debunked the claim that Y-carrying sperms are more fragile. They concluded that there was virtually no distinct difference between X- and Y-carrying sperms except for the content of their DNA.

"There's really not much you can do at home to choose your baby's gender," sums up Dr. Steinberg. If you're really determined to have a female, there are medical procedures involving sperm or embryo sorting that hold more promise, but their ethics are being debated on all fronts.

Some call this trend "embryo shopping" and point out that it is unethical to play with genes to choose characteristics like sex and eye color. But others say that if the science is also being used to weed out disease, then it might be worth it.

It's also important to note that while the question of a baby's sex is often limited to male (XY) versus female (XX), there are more chromosomal options that occur in nature. According to Planned Parenthood, the statistical chance of having a baby that is intersex is roughly 1 or 2 in 100 people born in the United States.

The Intersex Society of North America defines intersex as "a general term used for a variety of conditions in which a person is born with reproductive or sexual anatomy that doesn't seem to fit the typical definitions of female or male." Defining who is and who is not intersex can be very tricky and, just like predicting between female and male, can't be foreseen by folklore.

While science may not support the superstitions around sex selection and prediction, there is certainly no harm in having a little fun by experimenting anyway.

Editor's Note

While this article occasionally uses the terms "gender" and "boy" vs. "girl," it's important to note that gender is a personal identity that exists on a spectrum, can change over the course of a person's lifetime—and most importantly—is something that a person defines for themselves. Sex, on the other hand, is assigned at birth based on the appearance of a baby's genitalia. While sex assigned at birth often matches a person's gender (called cisgender), sometimes, for transgender, intersex, and gender nonbinary people, it does not.

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