Can You Predict Baby's Gender based on Heart Rate?

So you're pregnant. You've entered a world of novelty, nerves and excitement—learning to navigate your way with the help of friends, family and doctors. And while gender-neutral showers and baby names are trending, many expecting parents still want to discover their baby's sex as soon as they can.

So it's easy to get excited when friends tell you about less official ways to guess the gender of your baby. You may have heard the heartbeat theory: that the baby's heart rate can predict their sex. But is there any truth to this or is it simply a myth?

The heartbeat myth

Sorry eager parents but this old wives' tale is a myth. The idea is that if your baby's heart rate is above 140 beats per minute (bpm), you can expect that you're having a girl. If it's under 140 bpm means you're likely having a boy.

While the origins of heartbeat gender prediction are unclear, it has stood the test of time—existing as one of the most widely known pregnancy myths passed on over generations. Dual board-certified OB/GYN Dr. Greg Marchand says the normal range for babies' heartbeats is 110 to 160 bpm. He has had many patients ask him about the heartbeat theory, which he informs them is "100 percent a myth."

What the research says

Regardless of how far back this tale goes, there has never been much research to support it.

A study from 2006 reveals there are no significant differences between male and female fetal heart rate (FHR) during the first trimester. A 2011 study showed a slight difference in FHR based on gender, with girls having a slightly higher average heart bpm than boys, but not significant enough to bring validity to the heartbeat theory. A more recent study in the OBGYN community from 2018 found that male fetuses show a notably lower baseline fetal heart rate and greater variability compared to female fetuses. With that said, the differences are small and do not guarantee clinical significance.

Genetic counsellor Chelsea Wagner says that she has heard quite a few rituals and myths about predicting the sex of a baby, agreeing with Dr.Marchand on the validity of this one. "I'm not aware of any science that links rate of heartbeat to fetal sex prediction," she says

Other gender prediction myths

The heartbeat theory is one of many old wives' tales about how to predict gender.

"I think where these myths are rooted is the desire to know more about your baby and kind of celebrate something exciting—something you don't necessarily have control over," she says. "It truly becomes your baby with that extra information."

Belly shape is another common example with no scientific evidence to support it. The idea is that a high and round pregnant belly means a girl and a low and wide belly means a boy. But body shape, muscle tone and the baby's position are what determine the mother's belly shape, not the baby's sex.

Some of these myths date hundreds of years back too. For instance, the Ancient Chinese Gender Predictor Chart is more than 700 years old and determines gender by converting the mother's age and date of conception to the Chinese lunar calendar. Thereafter, the data must be cross-checked on a chart that predicts the baby's sex. Despite anecdotal claims that this method works, there are no scientific studies to back it up.

Dr. Marchand says that he has had patients come to him with their determinants of why their baby is a boy or a girl. "A lot of patients have come to me and said things like 'I know this one's a boy because it feels like my last pregnancy,'" he says. This is also in line with the myths; there is no scientific evidence to confirm that similar symptoms between pregnancies are an indicator of the same sex.

Reliable ways to learn your baby's gender

While old wives' tales can be fun, they're rarely reliable.

Ultrasounds and non-invasive prenatal tests (NIPT)—drawing the mother's blood to get the baby's DNA—are the only proven way to determine your baby's sex, says Dr. Marchand. "The ultrasound is very reliable after 17 weeks, but the most reliable is going to be NIPT which can be drawn as early as 10 weeks of pregnancy," he notes.

Wagner discusses how NIPT testing looks at sex chromosomes and chromosomes that can have an impact on the baby's health, such as if there are extra or any missing. "During development, even early on in the pregnancy, the placenta sheds some of its genetic information in some of those chromosomes, so they're actually floating around in the maternal bloodstream," she says.

You can also do an NIPT test at home. For instance, the SneakPeak Early Gender Test, can be found in drug stores, as well as online.

Dr. Marchand says that NIPT tests are very close to the medical-grade ones used in hospitals and have a 98 to 99 percent accuracy rate. While he advises expectant mothers to rely on these tests if they desire to know about their baby's gender or health before birth, there are some non-invasive tests he advises against, such as a fetal Doppler.

"I encourage patients to only worry about fetal movement. Only medically trained professionals know how to use Dopplers and it's very easy to scare yourself or have unnecessary visits to the ER if you're at home trying to listen to your baby's heartbeat with it," he says.

What the heartbeat can actually tell you about your baby

While the fetal heartbeat ultimately cannot properly inform you of your baby's sex, there is a lot of important information that can be obtained from it.

Dr. Marchand says that he uses the fetal heartbeat a lot as an obstetrician. "We look at the variability in the heartbeat, meaning how much the heartbeat changes from beat to beat, minute to minute," he says. "That's one of the main ways we tell if a baby is well oxygenated since we don't have a way to get in there and see what the baby's oxygen levels are."

Experts

• Dr. Greg Marchand, OB/GYN
• Chelsea Wagner, Genetic Counsellor