Gender prediction: Am I having a boy or girl?

Keep in mind, much of the scientific evidence here is slight, and some of it is hotly debated by experts. But it's still fun to try to guess. Read on to see what the statistics say for you. (Or try our Chinese gender predictor.)

Note: We're using the word gender here because people often use it interchangeably when talking about their child's sex. However, the two are not the same. A child is generally assigned a sex at birth based on biological characteristics, such as their genitals. But their sex designation may not match the gender identity (based on feelings and behaviors) that they assume later.

Signs you're having a boy

You may be slightly more likely to be carrying a boy if:

You and your partner are married or living together

One large study looking at data from 48 million births in the United States found that married couples are more likely to give birth to sons.

Another study of 86,000 parents showed that couples who were living together when they conceived were slightly more likely to have a boy.

Just over half (51.5 percent) of couples living together when they conceived (or at the time of their first prenatal appointment) had a boy, compared with 49.9 per cent of those who were living apart. The study's authors had no theory on why living together resulted in more boys.

You've been living together for less than a year

If your relationship is still new and exciting, you're more likely to be having lots of sex – and frequent sex may give male sperm a slight advantage.

Why? Male sperm are lighter and have smaller heads and shorter tails. This allows them to swim more easily through the slightly less hospitable mucus in your vagina at the beginning and the end of your fertile window. Some experts think that female sperm are more likely to reach the egg in the middle of your fertile period.

So if you're having frequent sex, you have higher odds of having sex during both the start and end of your fertile window, when male sperm have a slight advantage.

You eat well

One study divided 740 British women into groups according to their caloric intake. Of the women who had the highest daily intake (about 2,413 calories), 56 percent had boys. Of the women who had the lowest intake (about 2,283 calories), only 45 percent had boys.

Another study looked at 68 million births and found that women who gained more weight during pregnancy were more likely to be having boys.

Male fetuses are more fragile and are statistically less likely to be conceived or survive pregnancy when food is in short supply. Female sperm are more robust and baby girls are hardier early in pregnancy, so in leaner times they may be more able to survive.

You conceived in the summer

In some countries, more boys are conceived in the summer and more girls are conceived in winter.

This may be because more viral and bacterial infections are around in the winter. As male sperm and embryos are more fragile, they may be less able to withstand the mother's catching an infection than female embryos.

You have gestational diabetes

Women carrying boys have a higher risk of developing gestational diabetes. Exactly why isn't clear, but it's possible that male fetuses interfere with cell functioning that affects glucose metabolism.

Signs you're having a girl

You may be slightly more likely to be carrying a girl if:

You're over 35 years old and the dad-to-be is over 40 years old

The older the dad and mom, the more likely female sperm are to fertilize the egg. This could be due to hormonal changes in the woman as she ages. And older men produce fewer male sperm.

Or it could be that older couples are more likely to have sex in the middle of the fertile period, when female sperm may have the edge over male sperm.

You suffer badly from morning sickness

You're slightly more likely to have a baby girl if you have (severe morning sickness hyperemesis gravidarum).

A review of 13 studies found that 55 per cent of babies born to women who'd had severe morning sickness were girls. This was compared to 49 percent in the control group who didn't suffer from it. Some experts think that this is due to high levels of the hormone estrogen, which is linked with morning sickness.

It's very hot – or cold – where you live

A study of Japanese births from 1968 to 2012 found that more girls were conceived during a particularly hot summer in 2010, and again during an extremely cold winter in 2011.

Other research has shown that warm temperatures appear linked to girl babies. And a global survey of birth data showed that more girls are born in the tropics (the region around the equator) than anywhere else in the world.

One theory is that weather extremes cause stress. In addition to the uncomfortable temperatures, very hot or cold places tend to have poor nutrition, high levels of pollutants, and insufficient or excessive sunlight. Such stress is especially hard on male fetuses, which are more fragile than female fetuses in the earliest months of pregnancy.

Your job is stressful

Women working in mentally stressful jobs outside the home may be more likely to have a girl. A study looking at more than 16,000 births in a British hospital found that among women with jobs considered highly stressful, 53 percent had a daughter. In comparison, 46 percent of women with jobs considered less stressful had a daughter.

The dad-to-be's job involves pollutants or stress

A few studies have looked at the dad's occupation and the baby's gender. They found that dads with jobs that involve stress or pollutants seem to end up with more girls.

Though they were small-scale studies that looked only at certain occupations, dads with the following jobs had more girls than average:

• professional driver
• deep-sea diver
• submarine sonar technician
• flour mill worker
• high-performance pilot

You conceived after hormonally induced ovulation

Some studies carried out among women who used hormones to induce ovulation show that you are slightly more likely to have a girl if artificial hormones, such as clomiphene, are involved. However, other experts aren't convinced.

You already have two or more children

It's possible that the more children you have, the more likely you are to have a girl. This may be due to the fact that the more pregnancies you have, the higher your levels of the hormone gonadotrophin. Some experts have claimed that these higher hormonal levels could be linked to an increased chance of having a girl.

You're past your due date

Moms who give birth to girls tend to have slightly longer pregnancies. Boys are more likely to be born before their due date. After the 40-week mark, however, the odds slightly favor a girl.

Heart rate gender prediction

You may have heard that if your baby's heart rate is less than 140 beats per minute you're having a boy and if it's more than 140 beats per minute you're having a girl.

But researchers have 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 higher than for boys, the differences were small.

A normal fetal heart rate ranges from 110 and 160 beats per minute and can vary by 5 to 25 beats per minute. It may change as your baby responds to conditions in your uterus.

More about babies and gender

Get an inside look at how girls and boys develop

Can parents choose to have a boy or a girl? Find out what folk wisdom claims – and what scientists say

When your baby is intersex

Take our poll and find out who wants to know their baby's sex before the birth