Friends and family may point out signs of having a girl or boy, but most of these will probably be based on folklore rather than science.
An ultrasound at 20 weeks into the pregnancy is the most reliable way to tell a baby's sex.
This article discusses some of the traditionally held signs that someone is having a girl, as well as whether they have any scientific evidence to support them.
Eight signs of having a girl
We look at the science behind eight traditional signs of having a girl:
1. Severe morning sickness
Severe morning sickness may be a sign of having a girl.
Some people think that severe morning sickness is a sign of having a girl. In fact, recent research suggests that feeling ill during pregnancy may be linked to the baby's sex.
This difference may impact the way women carrying girls experience morning sickness. They may feel more unwell than those carrying boys.
More research is needed to fully understand if there is a link between morning sickness and a baby's sex.
2. Extreme mood swings
Hormonal changes during pregnancy can often cause mood swings. Some people think that women carrying girls have higher levels of estrogen and are moodier as a result. Research does not support this theory, however.
Hormone levels rise during pregnancy and fall after giving birth regardless of whether the baby is male or female.
3. Weight gain around the middle
If a woman gains lots of weight around her middle during pregnancy, some people think this means she is having a girl. They may also believe that gaining weight just in the front of the body indicates a boy.
Again, scientific evidence does not back up this theory. Where a woman gains weight in pregnancy depends on her body type.
4. Carrying the baby high
Carrying the baby high is an often-repeated sign of having a girl. Despite its popularity, this has no scientific basis.
Where a woman carries her baby depends on her:
- body type
- weight gain
- fitness level
- muscle strength
5. Sugar cravings
Women often experience new cravings when pregnant. Some people think if a woman craves sugar, she may be carrying a girl, whereas salty cravings may indicate a boy.
There is no scientific evidence to suggest that food cravings during pregnancy can indicate the sex of the baby.
6. Stress levels
If a woman has high stress levels before conceiving, she may be more likely to have a girl.
In this study, women with high levels of cortisol were statistically more likely to have a girl.
A 2013 study found that in the two years following an earthquake on the Greek island of Zakynthos, the male birth rate dropped. Researchers suspected that increased stress levels in the island's community affected the birth ratio.
More research is needed to properly understand the link between stress and the sex of unborn babies.
7. Oily skin and dull hair
Some people believe that having oily skin and dull hair may mean a woman is carrying a girl.
This belief is not scientifically based.
On the other hand, changes in oil production or hair appearance during pregnancy may relate to hormonal changes or changes in diet.
8. Baby's rapid heartbeat
Some people believe that if the baby's heart beats rapidly, they may be female.
However, researchers debunked this myth decades ago in a study that found no significant difference between the heart rate in male and female fetuses.
How doctors test for the baby's sex
The best opportunity to find out a baby's sex is when the doctor carries out an ultrasound scan at 20 weeks.
The doctor will look at the baby's genitals during the scan to determine their sex. This is usually accurate but not always, as many things can obscure the ultrasound image.
There are some other procedures the doctor can perform to get a definitive answer, including:
- chorionic villus sampling
- noninvasive prenatal testing
A doctor will usually only offer these procedures if they are concerned about the health of the baby.
Most anecdotal signs of having a girl are myths that need debunking.
Excessive morning sickness and preconception stress may mean it is more likely a woman will have a girl, but much more research is needed to understand fully how these factors influence a baby's sex.
The most useful way to determine a baby's sex is to ask for the doctor's professional opinion at the 20-week ultrasound.