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Morning Sickness: Boys vs Girls - Complete UK Guide

The Old Wives Tale

One of the most common pregnancy myths in the UK is that severe morning sickness means you are carrying a girl, while mild or no sickness means a boy. Generations of grandmothers, aunties, and friends have repeated this claim, and it is one of the first things people often say when they hear how unwell you have been.

But is there any truth behind it?

What the Research Actually Shows

There is a small amount of scientific evidence behind the myth - but it is far weaker than most people think.

Some studies have found that women carrying girls are slightly more likely to experience severe nausea and vomiting. One often-cited study found that women admitted to hospital with hyperemesis gravidarum were marginally more likely to be carrying girls than boys. The suspected reason is that female pregnancies produce slightly higher levels of hCG on average.

However, the difference is small - usually only a few percentage points. Plenty of women carrying boys have severe sickness, and plenty of women carrying girls have none at all. The link is not strong enough to predict your baby sex with any confidence.

Why People Believe It So Strongly

The myth persists because of how human memory works. If you had terrible sickness and later had a girl, the story confirms what everyone expects, and it gets repeated for years. If you had a boy despite being very sick, that story tends to be forgotten or explained away.

This is confirmation bias - we remember the cases that fit the pattern and quietly ignore the ones that do not.

What Actually Determines How Sick You Feel

Your baby sex plays at most a tiny role. Far more important are:

  • Your hormone levels overall (which vary hugely between pregnancies)
  • Whether you are carrying twins or more
  • Whether this is your first pregnancy
  • Whether you are prone to motion sickness or migraines
  • Your age and general health
  • Stress, tiredness, and diet
  • Genetics - some families have stronger sickness across generations

What About Other Gender Prediction Myths?

Many other claimed signs of a baby sex are equally unreliable:

  • Carrying high or low - related to your body shape and muscle tone, not sex
  • Heart rate - a baby heart rate changes through pregnancy and does not indicate sex
  • Cravings for sweet or savoury foods - unrelated to whether you are having a boy or girl
  • The shape of your bump - determined by your build and the baby position

None of these have evidence behind them.

How to Actually Find Out the Sex

If you want to know whether you are having a boy or a girl, the only reliable methods are:

  • The 20-week anomaly scan, if your sonographer can get a clear view and you ask to be told
  • NIPT (non-invasive prenatal testing), a blood test from around 10 weeks that can detect the baby sex with high accuracy
  • Amniocentesis or CVS, diagnostic tests usually performed for other medical reasons

A Balanced Takeaway

If you are very sick, it is perfectly natural to wonder whether it might mean you are having a girl. The truth is that you might be - or you might not. The severity of your morning sickness tells you much more about how your body is responding to this particular pregnancy than it does about the sex of your baby.

Enjoy the guessing games for fun, but do not paint the nursery based on how nauseous you feel. The only way to know for sure is through a scan or a reliable test.