When you're expecting a baby, the gender guessing game can be an exciting one. With so many theories and old wives’ tales available at the click of a mouse, it's easy to become swept up in trying to determine your child’s sex, but can you really tell whether to paint your nursery pink or blue from your scan pictures? Dr Geetha Venkat, Director of the Harley Street Fertility Clinic sets the record straight.


12-week scan

When it comes to your dating scan, usually performed at around 12 weeks, Dr Venkat is sceptical about the likelihood of an accurate prediction.

“12 weeks is rather early and even an experienced sonographer could not confidently identify the sex of a baby at this stage,” she states.

“The ideal time to look into this is during the 14th or 15th weeks of pregnancy when the baby’s sexual organs have grown to a point at which they can be correctly identified.”

“Up until this point, these look very similar and spotting whether they are internal or external can leave the results inconclusive, hence why it is vitally important to do this at the right time to avoid any inaccurate outcomes.

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"At the proper stage within the pregnancy, a boy’s testicles and penis can be seen clearly and so can a female’s labia.”

Rumours and myths

On message boards and internet forums, rumours abound on how to predict your child’s gender from scan images - what are the theories?

1. Nub theory

In the early stages of your pregnancy, the foetus’ genitalia, regardless of gender, can be seen as a small protuberance in the groin area.

Many mums-to-be are convinced that the angle that this nub is resting at (the 'angle of the dangle') at their 12-week scan, can determine the sex of the child.

According to Dr Venkat however, this doesn’t really carry any scientific weight. “As mentioned before, up until a certain point a male and female baby’s sexual organs will look very similar,” she points out, “so telling if they are protruding or internal is very difficult until they are sufficiently developed.”

2. Skull theory

Another popular theory that says you can tell your baby's sex from the shape of their skull on the 12-week scan. Square, big, stocky?

Or smaller compared to the rest of the body? Some say if you look closely this will give your baby's gender away.

3. Three lines

Far from being seen as just a theory, the three lines or 'potty shot' on a scan are actually often use my by midwives to tell the sex of your baby and is pretty accurate.

The difference between this one and the others mentioned, though, is that you'll need to wait until your 20-week scan to see it - or perhaps 16-week scan if you go to a private clinic.


Factors that affect your scan

When you do go for a later scan, during which your sonographer should be able to confirm the baby’s gender if you wish, there are a few variables to take into account, according to Dr Venkat.

“Sometimes identifying the sex of the baby can prove very difficult if the baby is not co-operating. If their legs are crossed it is impossible to see the genitalia which obviously determine if the foetus is a boy or a girl. If this happens, it is a case of trying to encourage the baby to move. We have asked mums to go for a walk and come back to see if the activity helps the baby into a new position, which usually works and then we can try again!

“A good ultrasound machine is vital when looking clearly at a baby and imaging has become very sophisticated, even allowing parents to see their baby’s facial expressions. But having an experienced sonographer is also a must to ensure an accurate identification.”

What about telling the gender from a 3D or 4D scan?

Even though 3D/4D scans might give you a better picture of what your baby looks like, experts agree that it can actually be harder to tell the sex from them, in part because it's recommended you wait until 28 weeks to have one - by which time it can be hard to see the genitalia.

Real mums share their gender prediction experiences on our forum

“We found out with our first that we were expecting a girl, but this time around we wanted to keep it a surprise but both me and my other half are sure we saw a willy at our 20 week scan. We’ll soon find out if we are right or not.” Hannahmummyto2

“It is hard to tell when you're not sure what you're looking at, and baby might have its legs crossed, or be moving around too much for you to get a good look so don't read too much in to it. I'm sure it'll be fun to look and speculate!!” lynz_81

“I was told my first was a boy, so I was very surprised when a beautiful baby girl popped out! I'm not sure what happened, I was told by the sonographer she was 80% sure it was a boy.” bride-carly-barleyx

“Depends which website you use as to what sex the baby will be! Some say use your age at conception, some say at birth and some say you have to use your age as in the Chinese calendar which can be different... So basically nothing works except getting the sonographer to tell you!” diggys_mum

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