Last reviewed by Dr Philippa Kaye and scan expert Gill Harrison: April 2024


Most of us wait until our 20-week NHS ultrasound scan to find out the sex of our baby (although the sonographer carrying out your scan may not always be able to tell even then). But we know that can be a long time to wait! If you're desperate to know sooner, there are lots of gender prediction tests and theories that will apparently reveal your baby's sex before then – but their accuracy varies wildly and very few have a properly scientific stamp of approval.

When will I find out if I'm having a boy or a girl – for sure?

"It can be possible to identify male and female genitalia at the NHS 20-week scan or at a private scan from about 16 weeks of pregnancy," says Dr Philippa Kaye, our expert family GP. "At most (but not all) NHS hospitals, the sonographer will tell you the sex at the 20-week scan, if they can tell and you want to know. There are also some other antenatal tests which you may be offered, such as non-invasive prenatal testing (NIPT), that can reveal the genetic sex of your baby. But this information may not be disclosed to you in an NHS hospital (it's not the clinical reason for the test), although you can choose to be told if you have this test at a private clinic."

Are there any signs and tests I can do earlier in my pregnancy to find out the sex of my baby?

Yes, there are plenty. But most of them really aren't very accurate, and many of them have no actual basis in science at all. But they're all interesting to do – and we know that plenty of people enjoy doing them and finding out the results.

We've identified below 30 of the most common boy/girl signs and tests. And we've grouped them loosely, by type of sign, into:

More like this
  • early scan signs
  • the heartbeat sign
  • telltale body signs
  • signs from home tests
  • predictions from dates and charts
  • emotional signs
  • traditional signs passed down the years

Do take them with a pinch of salt. "For the majority of these, there isn’t evidence that they work," says Dr Philippa, "but they might be fun!" So get out the baking soda, assess the angle of the dangle, count corvids and watch how you pick up your keys – but don't order your gender reveal cake on the results...

Here are 30 signs that could predict if your baby's a boy or a girl


couple checking scan picture of their baby

While, as we've seen above, it's the 20-week scan that will most reliably reveal your baby's sex, there are various theories and methods that are said to tell you if your baby is a boy or a girl by looking at scan you have done earlier in your pregnancy – either your NHS 12-week 'dating' scan or a 'gender-reveal' scan you may have booked at a private clinic, from about 16 weeks...

1. The Nub Theory

This boy or girl prediction involves looking at an early scan and making a note of the rather intriguingly named 'angle of the dangle'.

This is all about how the nub or bump of your baby's genital tube (the very early beginnings of your baby's genitals) is angled, compared to your baby's spine. According to the Nub Theory, if the angle between the base of the spine and the nub is less than 30°, it's a girl; if it's greater than 30°, it's a boy.

However, the reliability of this test is pretty low, especially if it's done on a 12-week scan. "Up until your 14th or 15th week, the female and male genitalia simply look too similar to 100% differentiate between the two," says Dr Geetha Venkat, Director of the Harley Street Fertility Clinic. "This can potentially lead to inaccuracies."

So, get your protractor out by all means but don't dangle all your hopes on the angle you're measuring.

2. The Skull Theory

This scan-based boy/girl prediction theory is based on the assumption that a boy's skull and a girl's skull look different – and that you can see that in a scan picture. It assumes that a boy's head and facial features will be bigger and blockier than a girl's, and that there are some telltale points of difference in the shape of the cheekbones, jawbone and forehead.

But before you start analysing your 12-week scan picture, be warned that, according to Christoph Lees, Professor of Obstetrics at Imperial College London and a faculty speaker for the International Society of Ultrasound in Obstetrics and Gynaecology, "there is no scientific evidence that it works".

In fact, most experts would agree that any differences between male skulls and female skulls don't develop until after puberty – so a few more years yet for that baby in your belly. And, for this reason, Kristina Killgrove, a bioarchaeologist, science writer and research scholar at the Ronin Institute, says that the theory makes no sense whatsoever. "Until you get to maturity, or at least puberty," she says, "you just don't get these sexually dimorphic features of skulls in males and females."

3. The Ramzi Theory or Ramzi Method

The Ramzi Theory (or Method) is said to be able to predict if you're having a boy or girl based on where your placenta is positioned in your uterus as early as 6 weeks into pregnancy. This is something that can be seen on an early transvaginal scan or at the routine 12-week scan.

The theory goes that, if the placenta is on your right, you're having a boy; if it's on your left, you're having a girl. Author of the theory, Dr Saam Ramzi Ismail, claims his method is 97% accurate but his findings were based on a very small number of women. What's more, his study was not published in a peer-reviewed article and it has not been replicated.

"There is no scientific research behind this," says Professor Lees, "and, given that many placentas are neither on the left nor the right side, it is highly improbable that this theory has any validity at all."

4. The 3 lines or 'potty shot' or 'hamburger sign' method

Now, this is the scan sign that you can most confidently rely on. It's the method used by NHS sonographers at your 20-week scan to see if you're having a boy or a girl – and private clinics tend to use it, too, when you book a 'gender reveal' scan from 16 weeks.

The reason it's called the 3 lines – or the 'hamburger sign' – method is that, during your scan, depending on how far you are on with your pregnancy and whether or not your baby's in a position that allows the sonographer to view from underneath (the 'potty shot'), the sonographer may be able to see 3 white lines (the clitoris, surrounded by the 2 lines of the labia) that usually means your baby is a girl.

If your baby is a boy, it can be possible to see the clear outline of his (differently shaped) genitalia in the same way.

This method is the most accurate method of predicting your baby's sex. However, you won't be given any cast-iron guarantees. As Gill Harrison, professional officer for ultrasound at the Society and College of Radiographers, says, "Even if the 3 lines are identified, it is still only an opinion from the sonographer – albeit a reasonably accurate opinion."


5. Horse or train heartbeat

At your antenatal appointments (though this less routine early in your pregnancy than later), you may find your midwife uses a handheld Doppler device to listen to your baby's heartbeat. If you do hear your baby's heartbeat, listen hard: does it sound more like a galloping horse or a runaway train? If it's a galloping horse, so the theory goes, you're having a girl; if it sounds like a train, you're having a boy.

Some people have refined this heartbeat theory further to say if your baby's heartbeat rate is under 140 beats per minute, it's a girl, and if it's over 140 beats per minute, it's a boy.

But according to Dr Philippa and a 2005 US study published in the journal Fetal Diagnosis and Therapy, there is no evidence that there's a significant difference between a boy and girl's heartbeat rate during the 1st trimester of pregnancy.

"A baby's heart rate will be somewhere between 110 and 160 beats per minute – much faster than an adult's," says Dr Philippa, "but that applies to boys and girls equally. There is no evidence that a heartbeat sounding like a train or a horse indicates either a girl or a boy."


pregnant woman in yellow dress

A large number of signs and tests that are said to predict if your baby is a boy or a girl are based around how your pregnancy is affecting your body. Changes to your skin or hair, and what you bump looks like are all said to reveal your baby's sex. Although there is precious little clinical evidence to back these theories up, some people swear by them...

6. High or low bump

A classic 'sign' of what sex baby you're having is how you're carrying – in other words, if your bump is all out in front or more spread out around. A spread-out bump that sits high is supposed to indicate that you are carrying a girl, and a lower, more compact bump is said to show you are having a boy.

You'll definitely have strangers giving you their boy/girl predictions based on this one – but whether they are right or not will be about as accurate as any 50/50 guess as there is no scientific basis for this 'sign' at all.

7. Bad morning sickness

The theory with this one is that you can tell you're having a girl if you have bad morning sickness. The medical jury is out on this one but it's fair to say most experts are not exactly convinced.

"Pregnancy hormones can make women feel very poorly early on in pregnancy," says Dr Geeta, "and if your baby is a girl, there will be an increased level of oestrogen within your body, which can often lead to sickness. That said, I have seen many women suffering from bad morning sickness who have gone on to have boys, so this is not a definitive identification tool."

8. Shiny hair or dull skin

Some people think that specific changes to your skin and hair are indications of the sex of your baby. So, you get dull skin or acne with a girl, and with a boy, according to this theory, you get shiny hair.

In reality, there is no evidence to support these beliefs. It is true that pregnancy can cause changes to your complexion and hair condition but it doesn't follow that any pregnancy skin 'glow' means you're having a boy.

9. Breast size changes

If you're pregnant and your left breast is bigger than your right, this means you’re having a girl – apparently. And if it’s your right breast that is bigger, then – you've guessed it – you're having a boy.

Hmmm, there really is nothing scientific to back this up, so don't get fixated on spotting any differences in breast size. Your breasts may well go through lots of changes during your pregnancy but the sex of your baby won't be the cause.

10. Nipple colour

If you find your areolas (the 'bumpy' area around your nipples) become much darker than usual, then the theory goes that you're expecting a baby boy.

Thing is, the vast majority of women find their areola colour darkens during pregnancy but last time we looked the number of baby boys being born isn't vastly outnumbering the number of baby girls...

11. Dark lines on your belly

It's common in pregnancy to notice a darkish line (called 'linea nigra') stretching down your belly. If it only comes as far as your belly button, then it's said to be a sign that you're having a girl; if it stretches past your belly button, however, it's a sign you're having a boy.

There's no evidence to support this bit of pregnancy folklore but it's fun to keep track of your line and speculate.

12. Hair on your belly

Sprouting new hairs down the middle of your pregnancy bump is a sign you're carrying a boy, say the boy/girl-predicting crowd.

Well, unless we've completely missed a massive increase in the number of boy baby births compared to girl baby births, we're a bit sceptical about this one. And that's because most women get some kind of "snail trail" down their bump in the second half of their pregnancy. Of course, this can vary from a bit of fuzziness to some serious sprouting but it's pretty common nonetheless.

13. High or low blood pressure

Believe it or not, this theory says you can predict your baby's sex based on your blood pressure 26 weeks before conception. The theory is based on the findings of a 2017 Canadian study of group of Chinese women published in the American Journal of Hypertension, where the women with higher systolic blood pressure ended up giving birth to a boy and the women with lower systolic blood pressure gave birth to a girl.

So this one does have some science behind it – but it's worth knowing that the study was widely greeted with scepticism at the time. Geoffrey Trew, a reproductive medicine consultant at London's Hammersmith Hospital’s was quoted by the Telegraph as saying, "I would be very surprised that a BP measurement, which is notoriously variable, could dictate sex 26 weeks before conception. Some reptiles can have sex differences due to temperature changes at the time of early fetal growth but not 26 weeks beforehand."

14. Shape of your face

If your face is rounder and fuller, then you’re expecting a girl, this theory goes. Bizarrely, there's an additional detail that if your nose starts to grow or widen, it's definitely a girl – as she's trying to 'steal' your beauty!

Not the greatest way to set up a healthy mother/daughter relationship, and also has no evidence to back it up.



There are a few tests you can take at home that are said to predict if you're having a boy or girl. We've included the most well known ones here, including a 'chemistry' test with baking soda and others with pendulums, keys and feet...

15. The baking soda test

This gender-prediction test is all about using chemistry to help reveal whether you're having a boy or girl. It's based on observing how your urine (yes, you read that right!) reacts with baking soda. If, after you have poured some of your wee onto a couple of spoonfuls of baking soda, it fizzes, then you’re having a boy. If there's no noticeable reaction, it's a girl.

It's all meant to be based on the idea that your unborn baby can affect the acidity of your wee – but this test has no real scientific proof behind it.

16. The cupping hands test


This is a test Holly Willoughby demonstrated when she was presenting ITV's This Morning (above). She reckons you can tell if you're having a boy or a girl by the position of your hands when you use them to cup the sides of your bump.

If your hands curve round the side of your baby belly (top pic), it's a girl; if they go slightly inwards (bottom pic), it's a boy.

We're not entirely sure we can see the difference from Holly's demo, to be honest, and again, there's no scientific basis for this test but, well, you've a 50/50 chance of being right!

17. The key pick-up test

This one's a tricky one to do on yourself because it's a test of how you spontaneously pick up a key – but, once you know what it's looking for, it's hard to do it spontaneously!

But anyway, apparently, if you pick up the key by the round (handle) end, you're having a boy and if you pick it up by the narrow end (the bit that goes into the lock first), you're having a girl. Oh, and if you pick it up somewhere in between, then it's twins!

Obvious bunkum but again, you have a 50/50 chance of being right (if you ignore the twins bit)!

18. The reflexology test

This test involves putting the soles of your feet together and looking to see if a particular area on one foot is 'fatter' than on the other foot. The area to look at is the bit between the heel and the arch – which is apparently the area of the foot reflexologists believe to be related to the uterus.

If your left foot looks ‘fatter’ in that area, you’re having a girl (reflexologists see the left side as feminine); if the right foot looks fatter at that same place, you’re having a boy (reflexologists see the left side as masculine).

There are no scientific studies to verify the association between this area of the foot and your uterus, let alone the association between sides of your body and femininity/masculinity. But it's fun to do – and, when we've done it, there is always a difference!

19. The pendulum test

Jools Oliver (pictured below) famously gave this test a go with baby number 5. It's all about how a pendulum, held loosely, swings over your bump. Apparently, if the pendulum swings back and forth, you're expecting a boy. But if it moves in a circular motion, you'll be having a girl.

Jools did not reveal whether the pendulum gave her a correct prediction but, if it did work, there would have been some back and forth action, as her 5th child was a little boy.



Some of the gender tests that claim to be able to predict if you're having boy or girl are truly from the old olden days. They generally rely on calendars or date checks – and not a lot of scientific research...

20. The Chinese Gender Prediction chart

part of chinese gender prediction chart

This one's a calendar which is said to reveal the sex of your baby based on your lunar age (your age plus 1 year) charted against the month of your baby's conception.

To work out if you're having a boy or girl, according to this method, you'll need to cross-reference a few bits of info – such as your age at conception and the month you conceived.

The test has no scientific basis but you can have a bit of fun with it and get an answer that will have 50% chance of being right.

21. The Mayan calendar

The Chinese Gender Prediction chart has become pretty well known now. The Mayan chart is very similar, but not so mainstream.

It involves charting your age at conception and your baby's birth month – and looking at odd and even numbers. Fun to do but by no means accurate. I used this retrospectively on my 3 children and got a 0% success rate, I'm sorry to report!


Now we're getting deep into totally unscientific territory but there are some well-rehearsed theories that the state of your emotions in pregnancy could predict if your baby will be a girl or a boy. Here are the most well-known ones...


22. Mood swings

If you get severe mood swings when you're pregnant, it supposedly means you're having a baby girl. Although, considering the surge of hormones flowing through your body, we think you’d be hard pushed to find a mum-to-be who doesn't have times when she feel moody – and we're not seeing a huge flood of little girls, are we?

23. Dreams about girls or boys

Now this is a bit of an upside-down one. If you lie in bed dreaming about little girls, chances are you’re having a boy; and if you dream about boys, it’s a girl you’re likely to be expecting. Slightly perverse and completely unscientific but weird enough to get you thinking...


old women sitting in a row and chatting

As long as women have been getting pregnant, it seems there has been curiosity around what the sex of the baby will be, which is probably why so many theories and tests have sprung up to predict a boy or a girl and then been handed down the generations.

As you can imagine, none of them would pass the scientific-evidence test but if you want some interesting to try while you're waiting to find out if you've got a boy or girl for sure, these might just fit the bill.

24. The way you lie down

Apparently, what side you lie down on tells a lot about which sex of baby you're expecting: if you lie on your left, it’s a boy; if you lie on your right, it’s a girl. Hmm, with a growing bump you might end up switching from side to side anyway, so we're not sure this one's going to work...

25. Sweet or savoury cravings

Whether you're craving strawberries or salt-and-vinegar crisps is said to be a clue as to whether you're having a boy. Sweet stuff means you are having a girl and, if you crave salty food, it's a boy. Not sure where it leaves you if you are craving coal or other non-edible items but, without a clinical evidence base, it's all just guesswork.

26. Number of boys or girls in your partner's family

As your baby's sex is determined by the sperm, some say looking at your partner's family is an indication of whether you'll have a boy or a girl – especially if his male siblings and father/grandfather through the generations had all boys or all girls. There's no evidence to back this up but it's interesting to have a look and get to know your baby's family tree anyway.

27. Looking at your hands

Apparently how your hands look can be an indicator of whether it's a boy or a girl. Dry hands means a boy; soft hands means a girl. AND if someone asks for your hand and you give it to them palm down, it's a boy. Palm up = girl.

28. Counting magpies

As well as determining good or bad luck, watching the magpies can be said to hint at a boy or girl. The old nursery rhyme says that if you see 3 magpies, that's a sign of a girl, and 4 magpies is a sign of a boy. Bring on the corvids and shut your eyes quickly when you get to your preferred option!

29. Smelling of garlic

Eat a clove of garlic and, if the smell comes through your pores afterwards, you’re having a boy. If no garlic can be smelt, you’re having a girl. Hmmm, we'd like to see someone who's expecting a girl put this to the test!

30. Who instigated sex

If you instigated sex with your partner on the night (or day) you conceived, you're expecting a girl – apparently. If it was your partner, then it's a boy. Sceptical face.

31. Your partner's weight gain

We know that your partner can gain weight while you're pregnant (some call it a 'sympathy belly') but the old wives' tale says that if they put on significant weight while you're expecting, it means the baby is a boy. Again, no evidence for this so let him tuck in – or not!

Pics: Getty


About our author Becky Harrington

Becky is a freelance journalist who specialises in healthcare. She has been a journalist for almost 30 years, writing and editing for a range of titles including Nursing Standard and the British Journal of Midwifery. She has 3 children between the ages of 12 and 18.

Read more: