8 Scientific Signs That You're Having a Boy or a Girl

It’s certainly a lot of fun guessing when you’re expecting … and there’s no shortage of people willing to join in (you’re carrying a boy because you're carrying high in your belly, says one friend; you’ve got acne because you’re carrying a girl, says your mom). 

But you may be wondering if there’s anything, short of noninvasive prenatal testing and prenatal diagnostic tests like CVS and amnio, that can clue you in to your baby-to-be’s sex. The answer is yes — and no.

Findings from numerous studies yield clues that can point to an increased probability of which gender you’re carrying (though just as many gender prediction old wives' tales have no science to back them up).

While you shouldn't take the following findings to heart — they're still just for fun, and even the predictions that have been studied often tilt only ever so slightly toward one sex or the other — they may make the game of odds slightly more accurate.

Signs you might be carrying a girl

You’re suffering from hyperemesis gravidarum

Most moms-to-be experience some form of morning sickness when they’re expecting. But some moms have it much worse, suffering from severe nausea and vomiting (called hyperemesis gravidarum).  

Studies have found that women who are pregnant with girls may be more likely to experience nausea and vomiting during pregnancy. These findings were even more strongly linked to women who suffer from severe morning sickness. 

What’s to blame? The pregnancy hormone hCG, say researchers, which female fetuses produce more of than males. (Just don’t tell that to Kate Middleton, who has suffered from hyperemesis gravidarum during all three of her pregnancies with two sons and a daughter.) 

You’re extra forgetful

For reasons unknown, some research suggests that women who give birth to girls consistently under-perform in tests of memory — specifically in areas of listening, computational and visualization skills — compared to moms carrying boys.

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So the next time you can’t remember where you put the car keys, you may be able to blame your pregnancy brain on the baby girl you’re carrying.

You’re under a lot of stress 

The more stressed out you were when you conceived, the more likely it is that you’ll have a girl, say researchers. That's because girls may be less vulnerable to unfavorable conditions in the womb than boys are.

One small 2019 study, for example, found that moms-to-be who reported experiencing physical and psychological stress were more likely to give birth to daughters.

Your baby is breech 

Are you past 32 weeks pregnant and your baby is still stubbornly bottom-down, head-up? It may be time to think pink! A 2015 study of all singleton breech births in Hungary between 1996 and 2011 found that breech babies are significantly more likely to be girls than boys.

Signs you might be carrying a boy 

You ate a high-calorie diet at the time of conception 

One study found that eating a high-calorie diet at the time of conception and eating regular breakfasts may slightly increase the chance that you’ll be having a boy. 

The researchers found that 56 percent of women with the highest calorie intake around the time of conception had boys, compared to 45 percent among women with the lowest caloric intake. The evolutionary thinking goes that sons require more resources (i.e. more calories) than daughters do, so a higher-calorie diet would favor a baby boy-to-be.

You’re eating more during your pregnancy

Is it a boy or a girl? Your appetite may offer a clue. One study tracked the diets of moms-to-be and found that women who were pregnant with boys ate about 10 percent more calories than those who were pregnant with girls. 

Why the greater appetite? Researchers suspect testosterone secreted by male fetuses could be sending their mothers a signal to eat more. And that could explain why baby boys tend to be bigger at birth than baby girls.

You’re revolted by formerly favorite foods

Got food aversions — even to ones that were favorites? Researchers say that the more disgust toward foods a pregnant woman feels, the likelier it is she’s pregnant with a boy.

The reason? Aversions are tied to the way a woman's immune system functions as she tries to protect her growing fetus. Squeamishness, say researchers, is designed to protect the especially vulnerable male fetus by causing the expectant mom to stay away from potentially sketchy substances.

You develop gestational diabetes 

Some research has found that moms-to-be pregnant with sons are more likely to develop gestational diabetes — a pregnancy condition characterized by higher-than-normal glucose in the blood — than expectant moms who are pregnant with daughters. 

Researchers aren’t sure why a boy fetus leads to greater pregnancy-associated metabolic changes than a girl fetus does, but these findings seem to be backed up by more than one study.

What is the heart rate gender prediction?

There is one folktale, however, that scientists have studied — and it has to do with whether fetal heart rate can predict gender.

Conventional wisdom holds that if the baby’s heart rate is less than 140 beats per minute, you’re having a boy; if it’s more than 140 beats per minute, you’re having a girl. 

Medical research has debunked this heart rate gender prediction theory. A 2018 study of nearly 10,000 pregnancies found that while the baseline fetal heart rate of girls was very slightly higher than for boys, any differences they noted were very small and essentially not meaningful in the big picture. 

The truth is, a normal fetal heart rate fluctuates between 120 and 160 beats per minute. If you measure your baby’s heart rate at random intervals, it’s likely you’ll get a different reading each time.

The only time when there is an actual difference in heart rate between a boy and girl? It’s during labor itself, when female babies seem to have faster heart rates than males, for reasons unknown.

Gender prediction superstitions

As for all the gender-prediction folktales — the ones that claim to predict with certainty what sex you’re carrying? While they don’t have any science to back them up, they’re certainly fun to play around with. Here are some of the most common old wives' tales that claim to predict a baby's gender:

• Where you're carrying. If you’re carrying low in your hips, the theory goes, you're having a girl. If you're carrying high in your belly (like a basketball), you're having a boy.
• Position of the linea nigra. If your linea nigra (the line of pigmentation on your belly) runs only up to the belly button, some say you’re having a girl. If it runs past the belly button and up toward the ribs, it’s a boy.
• Nipple color. Darker nipples mean you’re having a boy, the legend goes. But in fact, pregnancy hormones cause most women’s nipples to darken (and maybe also become more tender), whether they’re having a boy or a girl. 
• What are you craving? Hankerings for sour, salty or protein-rich foods mean you’re having a boy. Can’t get enough sweets or fruit? It’s a girl. 
• You’re (really) moody. Is every day an emotional rollercoaster? Intense mood swings are thought to be a sign of a girl, while more even-keeled moods indicate a boy. (In fact, pregnancy mood swings are totally normal no matter your baby’s sex.)
• Where are my socks? Some believe that boys make your feet cold during pregnancy, but girls don’t. 
• What’s your pee color? Having a girl makes your urine darker yellow, while having a boy makes it lighter. The truth? Darker pee is a sign that you might be dehydrated — so drink up!
• Try the ring gender prediction test. Take your wedding ring (or another ring or needle) and attach it to a thread. Lie down, and have someone hold the dangling ring over your belly. If it swings in a circular motion, you’re having a girl. If it moves in back and forth like a pendulum, you’re having a boy.
• Chinese birth calendar. Check out the Chinese gender predictor chart (a.k.a. Chinese birth calendar), which predicts the baby’s gender based on your age and the month your baby was conceived.

Remember, predicting the baby’s sex ultimately has about a 50 percent chance of coming true. Aside from genetic testing, the only way to be 100 percent sure of your baby's sex is to wait until he or she is born. In the meantime? Try a few guessing games — and look forward to seeing how your predictions pan out!