Most old wives' tales about pregnancy are just fun myths passed down from one generation of mom to another. But there's one that might have a hint of truth to it, a new analysis of What to Expect data finds: If you're pregnant and nauseous, you're more likely to have a girl.
Editors at What to Expect analyzed the symptoms logged by nearly 118,000 moms on the app — and found that moms expecting girls do feel nauseous more than those pregnant with boys.
Here's what these new numbers mean, where that centuries-old belief comes from, and how you can know your baby's biological sex — for sure.
Pregnant and feeling nauseous? A baby girl might be on the way
The What to Expect app allows pregnant moms to log their symptoms and customize their profiles in various ways, including with their baby's biological sex. Many moms on the app record these symptoms throughout pregnancy, even before they know the sex of their babies.
As it turns out, moms expecting baby girls are more likely to report nausea during pregnancy than those with baby boys on the way, according to a review of more than 1.8 million symptoms recently logged on the What to Expect app. The symptoms were logged by a total of 117,730 pregnant users.
Specifically, girl moms are 3.2% more likely to log nausea or vomiting as a symptom than boy moms. Out of the 67 different symptoms pregnant moms can track on the What to Expect app, this is the largest absolute difference when looking at pregnancy symptoms and the reported sex.
Anecdotally, many moms in the What to Expect Community can vouch for this finding. "My boy, I was hardly ever sick," says member KarraMae. "With my daughter, it was every single day, even throwing up in labor."
"My first two children were boys and I never had morning sickness," adds member MudNMagnolias. "With my daughter, I was sick from the day I got the positive pregnancy test … Girls definitely make me sicker!"
Of course, some moms still have the opposite experience: "I had nausea with my son but not my daughter," says member 3xmama2026.
"I had severe nausea all day in the first trimester with my son," adds zeejaybee.
Why can morning sickness and nausea be linked to having a baby girl?
Anecdotal reports of a link between nausea and having a baby girl have been around for centuries — dating back to an ancient Greek book called Aphorisms by Hippocrates, says Caitlin Baulch, Ph.D., a faculty member at Wake Forest University who has researched old wives' tales.
The connection partially comes from people's observations, but other factors have likely made it stick around, experts say.
- Gender bias: "If you look at [the old wives' tales] which carry through to the 16th century and today, you'll notice that a lot of the 'bad' descriptions and symptoms are associated with having a girl, and the positive symptoms are associated with having a boy," Baulch says. "Some of it is observation-based, but also some of it maybe is just gender bias as well."
- Confirmation bias: Old wives' tales regarding gender prediction remain persistent because, no matter what, people end up being right about half the time, adds Jonathan Schaffir, M.D., an OB/GYN and expert of obstetrical folklore at the Ohio State University Wexner Medical Center in Columbus, Ohio.
- Statistical evidence: What to Expect's data builds on a 2021 study that looked at 4,320 pregnancies and had similar results.[1] Pregnant women who've had baby girls retroactively report experiencing morning sickness more often, says Max Krasnow, Ph.D., one of the study's authors and an instructor at the Division of Continuing Education at Harvard University in Cambridge, Massachusetts.
Why might having a baby girl make you more nauseous?
More research is needed on exactly why morning sickness is tied with a greater chance of having a baby girl, but experts theorize that it has something to do with hormones.
"Traditionally, nausea and vomiting in pregnancy have been linked to human chorionic gonadotropin, the hCG molecule, which is what people check when they're trying to find out if they're pregnant," Dr. Schaffir says. "The hCG levels have been higher in patients carrying female fetuses than with male fetuses."
When can you find out your baby's sex?
If you want to know for sure whether you're expecting a boy or girl, there are a couple of more reliable ways you can find out:
- Noninvasive prenatal testing (NIPT): As early as week 10 of pregnancy, this simple blood screening can detect your baby's sex and assess their risk for a number of genetic disorders.
- 20-week anatomy scan: This routine scan (sometimes called the level 2 ultrasound) measures your little one's size and analyzes the amount of amniotic fluid in your uterus. While the ultrasound tech checks your baby from head to toe, they'll take a look at your baby's developing genitals to see if your little bundle is a boy or a girl, so speak up if you don't want to find out just yet.
What can you do if you're nauseous during pregnancy?
If you're dealing with morning sickness, there are some ways to find relief:
- Snack more often. Because you're more likely to feel nauseous with an empty stomach, consider having a snack shortly after waking up. You can also try eating six small meals throughout the day rather than three large ones.
- Brush your teeth. In addition to keeping your dental health in tip-top shape, a minty-fresh mouth could reduce queasiness as well.
- Take your prenatal vitamins with food. If you suspect your prenatal vitamin is behind your nausea, try taking it with a meal. Don't be afraid to ask your doctor if a different prenatal would serve you better, either.
Nausea during pregnancy often goes away with time. Take it step by step, but don't hesitate to reach out to your doctor or midwife for help managing your symptoms.
The bottom line
Countless moms feel queasy during pregnancy and have a baby boy, Dr. Schaffir confirms. But if you're dealing with nausea or vomiting during early pregnancy, this statistic might give you something to hold onto during a weird but wonderful time.
"With my first pregnancy, having my son, [I had] no nausea or morning sickness at all," says Community member firsttimemama05. "With my second, nausea mainly started at 5 weeks and I’m 10 weeks now and it’s gotten better. Just think[ing] and hoping I’m having a girl since I'm having symptoms I didn’t experience with my son."
Methodology
What to Expect analyzed more than 1.8 million symptom logs submitted by 117,730 pregnant users on the What to Expect app between January 1 and June 30, 2025. Users self-reported symptoms throughout pregnancy, often before learning their baby’s sex, and later updated their profiles accordingly. The analysis compared the frequency of 67 tracked symptoms by reported fetal sex to identify any statistically significant differences. Findings reflect aggregated, anonymized user data and highlight trends across a large, real-world sample of pregnancies.
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