Can You Predict Your Baby's Sex?

How well can rings, dreams, or countenance foretell boy or girl? Some people swear by old wives' tales as foolproof methods for pregnancy prognostication.

Medically Reviewed by Melinda Ratini, MS, DO on April 02, 2024
5 min read

When you’re pregnant, chances are you’ll hear things like this – sometimes from total strangers: "You're carrying low. You must be having a boy." Or: "If you have morning sickness all day, it's definitely a girl."

There are even  odder myths for predicting the baby's sex. One suggests that hanging a wedding ring from a strand of the father's hair over their belly. Another suggests that you mix your urine with Drano; the color is supposedly a clue about your baby's sex.

Now that medical technology makes it possible to determine an unborn baby's sex with almost total certainty, why do these old tales persist?

The internet and social media are at least partly to blame for the ongoing pregnancy rumor mill. Myths fly through cyberspace, bouncing from one post to another at warp speed.

People reading those random comments can wrongly take them for medical facts. "Sometimes people take what's said online at higher value than what their physician says," says Sharon Mass, MD, an OB/GYN in Morristown, NJ, and clinical assistant professor at the University of Medicine & Dentistry of New Jersey.

Even though most wives' tales about guessing the baby's sex are harmless, "My medical caution to my patients is: Please make sure you know the source of what you're paying attention to or sharing," Mass says.

New parents -- especially those who are pregnant for the first time -- can be especially susceptible to pregnancy rumors, says Eileen Beard, senior practice advisor for the American College of Nurse-Midwives. "You're so concerned about doing the right thing and getting all the information. I think it makes you very vulnerable in a way. Even people who wouldn't normally believe myths are more likely to."

Another reason why sex prediction myths persist is that sometimes they can appear to be right. When you're looking at 50/50 odds, predictions are bound to come true half the time. And surprisingly, at least a couple of these methods do have some evidence to back them up.

Here's what experts say about a few of the most rampant baby sex prediction rumors.

Myth: If your belly hangs low (or in front), you're having a boy. If it's high (or wide in the middle), you're having a girl.

Reality: This one is pure myth. "How you carry simply has to do with the tone of your muscles and the position that the baby is in," Beard says. These factors, along with your body shape and how much weight you gain during pregnancy -- not the baby's sex -- will determine how low or high your belly sits.

Myth: If the baby's heart beats faster than 140 beats per minute, it's a girl.

Reality: This is a myth Mass says her patients ask her about on a daily basis, and there might actually be a wee bit of truth to it.

A 2006 study showed no sex-related differences in fetal heart rate during the first trimester, but Mass says that's no surprise, considering that babies' hearts beat faster in general during the first 28 to 30 weeks of pregnancy. It's later in the pregnancy when the difference becomes apparent. A 1999 study showed that just before delivery, a female baby's heart does beat faster than a male baby's. Mass says she sees a similar trend in her own patients.

Myth: Hang your wedding ring from a strand of the father's hair over your belly. If the ring swings around in circles, it's a girl. If it sways back and forth, it's a boy. An alternate version of this myth recommends dangling a pin over the mother's wrist.

Reality: There's no real evidence to confirm or deny this one. Mass doesn't see any scientific basis for it, but she says people who follow traditional Chinese medicine might explain the dangling ring (or pin) as evidence of the body's natural forces at work.

Myth: Stir some Drano into your urine. If the mixture turns green, it's a boy. Other color changes have been proposed for this myth, but green is one of the most common.

Reality: Mass doesn't know of any medical reason why a Drano-urine mixture could predict a baby's sex. "There's no change in the acidity or alkalinity of a boy or girl chromosome," she says.

The few studies that have been done on the subject also refute the claim. In the early 1980s, researchers at the University of Wyoming performed the test on 100 pregnant women and found it to be "roughly equivalent to flipping a coin" for predicting sex. A 1999 Canadian study yielded similar results.

Even if the technique did work, Drano is a caustic chemical -- not something you want to be playing around with or breathing in while you're pregnant, Beard says.


Myth: A pregnant woman who craves sweets is having a boy. If they crave sour foods, they're having a girl.

Reality: Your baby boy might grow up to have a sweet tooth, but while they're in your womb they're not going to make you desperate for an ice cream cone or candy bar. If you're craving sweets (or any other food), it's probably because your shifting hormones have intensified your sense of smell.

Myth: If you have morning sickness all day, it's a girl.

Reality: This myth might have some truth to it. Studies have found that women with a severe form of morning sickness called hyperemesis gravidarum are more likely to give birth to girls.

The reason? Levels of the pregnancy hormone hCG, which triggers morning sickness, tend to be higher in mothers who are pregnant with girls.

But anyone who’s pregnant can have morning sickness, even bad morning sickness, when they're carrying a boy. So no, you can't count on it being a girl if you've got serious morning sickness.

Myth: The Chinese lunar calendar can predict a baby's sex based on the mother's age when they conceived and the month of conception.

Reality: The Chinese lunar calendar was discovered in a 700-year-old Royal tomb, and many pregnant women who've used it swear by it. Could this ancient artifact have some modern science behind it? Not necessarily. According to the same Canadian researchers who did the Drano test, the lunar calendar is no more accurate at predicting a baby's sex (50/50) than a random guess.

If you’re curious about the sex of your baby, you can get an ultrasound, which is usually done between weeks 18-20 of pregnancy. Provided that your ultrasound technician gets a good view between your baby's legs, the imaging procedure should be able to tell you the baby's sex with about 80% to 90% accuracy.

Amniocentesis and chorionic villus sampling (CVS) also can determine your baby's sex with a high degree of accuracy, but these more invasive tests are usually reserved for situations in which the baby may have a genetic disorder or chromosomal abnormality, such as Down syndrome.

The genetic testing that many doctor's offices offer after 9 weeks of pregnancy also look at sex chromosomes and check on the sex of the baby with 99% accuracy.