Five Myths About Guessing Your Baby’s Gender, Busted By Science

Parents who can’t wait to find out their baby’s gender have options. Ultrasounds. Bloodwork. Amniocentesis. But many expecting moms and dads prefer to be surprised, which inevitably leads to a lot of “educated” guesses, most of which will be based on persistent myths and wives' tales. Old and wrong ideas about gender determination hold so much sway that people are constantly doing ridiculous things: Women pee in Draino and men consult the Chinese calendar or measure bumps. While most of this is harmless–and maybe even fun–it’s also important to retain perspective and understand that many of the “old-fashioned” means of determining sex are complete nonsense. That said, many does not mean all.

Here are five common myths about how to predict your baby’s gender, thoroughly debunked and two really weird peculiar old methods that, surprisingly, may actually have a basis in science.

Girls Have Higher Fetal Heart Rates

Even before your first ultrasound, your doctor will likely use a doppler heart monitor to measure your baby’s heart rate. If all is well, the heart rate should fall between 120 and 160 beats per minute. But ask around, and you’ll find that many people believe a heart rate closer to 160 means you’re going to have a girl, while a heart rate closer to 120 means you’re having a boy.

In 2006, intrepid scientists at Wright State University in Ohio examined nearly 1,000 sonograms from women in their first trimesters and second trimesters. Later, when the babies were born, they analyzed the average heart rate for boys versus girls and found that baby boys had an average heart rate of 154.9 beats per minute while baby girls clocked in at 151.7. Given that both averages were “plus or minus 22”, the authors concluded that there was no correlation.

Pee Into Draino To Predict Your Baby’s Gender

This is a weird one, but it’s been on scientists’ radars since at least 1982 when Dr. Robert M. Fowler, a physician at the University of Wyoming, tested whether women can predict their babies’ genders by having subjects pee into Draino. You can almost hear the exasperation in his voice: “During the past several years, we have been asked frequently to do the ‘Drano test’ to determine the sex of an unborn baby…Reportedly, the color green indicates a male baby, and yellow to amber indicates a female.”

In a way, aren’t we all Dr. Robert M. Fowler?

He had 100 pregnant women pee into a test tube of Draino and found no correlation between urine color and the gender of the fetus. Twenty-one of the urine samples didn’t even turn Draino one color consistently. And just in case Fowler’s work (and common sense) was insufficient to debunk this myth, Canadian scientists replicated the study in 1999, this time even more robustly: “Some health care professionals and patients believe that green indicates the fetus is male and brown indicates the fetus is female others, however, believe the opposite to be true,” they write. “Given the conflicting views, we examined both theories.”

They arrived at a new theory: Draino should be used in drains.

The Chinese Lunar Calendar Knows Best

Derived from the I Ching and reportedly kept secret for hundreds of years by a cabal of eunuchs, Chinese royalty is thought to have used a complex lunar prediction chart to ensure that the monarchy was always well stocked with baby boys. Now we have it. Does it work?

Not quite. The same Canadian researchers who convinced more women to pee in Draino for science also took the time to enter their participants’ birthdays and months of conception into the Chinese lunar calendar chart. They found that “the positive predictive values calculated for the Chinese calendar data were 50 percent.” In other words, the Chinese charts were about as accurate as flipping a coin—though coins were not historically hidden by eunuchs.

If Your Belly Looks Likes A Basketball, It’s A Boy…

Less occult than the I Ching but no less steeped in myth, there’s the idea that you can predict a baby’s gender by examining how the mother is carrying—whether her baby is all in front, like a basketball tucked under her maternity mumu, or evenly distributed around her hips. When scientists got around to debunking this one, the first problem was that nobody could even agree on what the myth claimed.

“There was a confusion in the sample as to which shape was associated with which sex,” researchers wrote. “Forty percent of women who rated themselves as carrying ‘all up front’ predicted they were having a girl; 57 percent predicted a boy.”

Not that it really matters. There’s no known relationship between either shape and baby gender.

Remember What You Ate Last Night? How About That Night?

This one might be tricky for exhausted parents who can’t remember what they ate for breakfast, but folklore and even some preliminary studies claim you can influence the gender of your baby even before you conceive by controlling your diet—boys, the myth goes, are born to mothers who eat the heartiest meals before getting it on. But a systematic review of the (surprisingly numerous) studies on the subject concluded that “this claim is pseudoscientific.”

Rough Pregnancy And Labor Can Predict Gender (Maybe!)

Women with severe morning sickness known as hyperemsis gravidarum may be more likely to have girls than boys. Scientists suspect this is because levels of the hormone hCG tend to be higher in mothers expecting girls and also trigger morning sickness. Other studies have called this link between morning sickness and baby girls into question, but it seems plausible.

Even better-established is the claim that women with long, difficult labors often deliver boys. A study of 8,000 births published in the British Medical Journal found that the average length of labor increased when delivering a boy—possibly because baby boys have enormous heads. It’s a late—and unpleasant—way to predict your baby’s gender, but at least it’s evidence-based.

Educated Women Just Kinda Know (Maybe!)

This is a weird one, and it definitely requires some follow-up. In 1999, Johns Hopkins researchers gathered 100 pregnant women who did not know the genders of their babies and asked them to guess, and explain their reasoning. One of the strangest results was that, when highly educated women with more than twelve years of schooling simply guessed the gender, they were correct about 71 percent of the time—less educated women were correct in less than 50 percent of cases. Even more unsettling, the authors report that women who based their guess on a dream about having either a male or female child were correct more often than women who based their guesses on common myths, such as heart rate or the Draino test.

If nothing else, this last result should give pause to parents who swear by folklore. When your method for predict a baby’s gender is less accurate than even dreaming—it’s probably off.