Many people claim that they can predict a baby's sex using signs such as the size of the mother's breasts or the position of the fetus in the womb. However, little scientific evidence supports these claims.
In this article, we look at the research into fetal heart rate as an indicator of sex. We also explore other myths about predicting a baby's sex and describe reliable scientific methods.
Can babies' heart rates indicate their sex?
Studies have found no connection between a fetus' heart rate and their sex.
Some people believe that the speed of the fetus' heart rate can predict the baby's sex.
For some, this may be an exciting idea, because a doctor can determine the heart rate from the first trimester before an ultrasound can show the baby's sex.
The belief is that a heartbeat slower than 140 beats per minute indicates a male baby, while a faster heartbeat indicates a female baby.
There is no evidence that this is true.
What the research says
A number of studies have looked for a link between a fetus' heart rate and their sex.
In 2006, one study found no significant differences between male and female fetal heart rates.
The researchers took the heart rates recorded on 477 sonograms taken during the first trimester and compared them to the sonograms taken during the second trimester, which the doctors used to determine the fetuses' sex. They concluded that a fetus' heart rate was not an indication of its sex.
In 2016, a study looked at 332 female and 323 male fetal heart rates recorded during the first trimester. These researchers also found no significant difference between them.
When can you find out the sex?
The only way to be completely sure of the sex of a baby is to wait until birth.
Healthcare professionals can make the best prediction during an ultrasound exam after 18 weeks. This procedure uses high-frequency sound waves to scan the abdomen and pelvic cavity.
A healthcare professional usually begins by applying gel to the abdomen, and the gel acts as a conductor for the sound waves.
They then use a piece of equipment called a transducer to send sound waves into the womb. The sound waves bounce off the baby's bones and are picked up by the transducer.
The equipment generates a black-and-white image of the fetus and placenta on a screen. This image is called a sonogram.
Pregnant women tend to have ultrasound scans between weeks 18 and 22 of pregnancy. This scan can help the doctor to:
- fix the due date
- look for twins or triplets
- check the position of the placenta
- look for signs of possible complications
They may also be able to predict the sex of the baby. However, the accuracy of this prediction can be influenced by many factors, such as the stage of the pregnancy and the position of the fetus.
The number of ultrasounds performed during pregnancy will depend on the healthcare provider.
Doctors may request ultrasounds at different stages for different reasons, according to the American Pregnancy Association.
During the first trimester, a doctor may use an ultrasound to:
- confirm the pregnancy
- confirm the heartbeat
- determine gestational age
During the second trimester, a doctor may use an ultrasound to:
- diagnose fetal malformation
- confirm multiple pregnancies, such as twins or triplets
- check on the well-being of the fetus
During the third trimester, a doctor may use an ultrasound to:
- check the movements of the fetus
- examine the position of the fetus in the womb
- identify any uterine or pelvic issues
Other myths about predicting a baby's sex
Many theories about predicting a baby's sex remain unproven.
Many popular myths surround the prediction of a baby's sex while they are still in the womb.
One involves tying the mother's wedding ring to a thread and holding it over the pregnant abdomen. According to the myth, if the ring moves in circles, the baby will be a boy. If it swings from side to side, the baby will be a girl.
Below are some other myth-based predictions:
A woman is more likely to be carrying a boy if:
- she is carrying her pregnancy bump in front
- she is carrying her pregnancy bump low down
- she did not experience morning sickness in the first trimester
- her right breast is bigger than her left
- she craves foods that are salty or rich in protein, such as cheese or meat
- her skin becomes dry
- her hair becomes more full-bodied and shiny
A woman is more likely to be carrying a girl if:
- the pregnancy bump extends around the abdomen
- she carries her pregnancy bump high
- she experienced morning sickness during the first 12 weeks of pregnancy
- her left breast is bigger than her right
- her cravings are for sweet foods, such as fruit and candy
- her skin gets softer
- her hair becomes thinner and duller
Many people enjoy toying with these theories and making predictions of their own. However, no scientific evidence supports their accuracy.
Many myths surround the sex of an unborn baby. One is that, early in pregnancy, unborn boys have faster heartbeats than girls.
There is no evidence that this is true. Studies have shown that there is no difference between male and female fetal heart rates.
A healthcare professional can make an educated prediction about a baby's sex during an ultrasound. This is only possible from around the 18th week of pregnancy. Even then, the baby's position can make a prediction difficult.
The only way to be sure of a baby's sex is to wait until they are born.