Skull theory: can it predict your baby’s sex at 12 weeks?

Baby scan photo

by Emily Gilbert |

There are dozens of old wives' tales that try to predict your baby's sex, yet many mums swear by the technique known as 'skull theory'.

Expecting mamas have been uploading their 12-week scan photos to try and get the internet to guess if they're having a boy or a girl with a quick analysis.

Traditional medical scans won't determine whether a baby is male or female until 20 weeks - but some experts think it is possible to predict the foetus' sex at 12 weeks.

What is skull theory?

Apparently, it's super easy to tell by analysing the skull shape and‘nub’ area between the legs. Boys predominantly have squarer chins, a chunkier skull shape and a more pronounced brow ridge, whereas girls’ skulls have a smaller brow ridge and more pointed chins.

Babies with a ‘nub’ – or genital tubercle – angled at greater than 30 degrees are likely to be boys, while girls' nubs sit below 30 degrees.

Skull theory accuracy

Some experts claim up to 88 per cent accuracy using the technique - making it more effective than the 75 per cent of parents who said their 20-week scan correctly predicted their baby’s sex.

Realistically, there's not enough evidence to support the skull theory's accuracy and the skull differences to determine sex tend to only be visible in adult skulls, not neonatal ones, making the theory, well, pointless.

"The Nub and Skull theory is the fastest-growing gender prediction technique simply because it’s so social," says gender expert Lisa Lum.

"Three-quarters of mums who try it say they like getting other people’s opinions on their child’s sex while 30 per cent see it as a worldwide craze they like to be part of.

"While no non-medical technique is 100 per cent accurate, it’s fun and brings people together, which is exactly what children should do at all ages."

Try out skull theory

Can you use the skull theory to try and guess whether Candace is having a boy or girl?

Candace gave birth to a boy! Did you guess right?

Mum Rhiannon also shared her scan picture below - can you guess what she had?

Rhiannon gave birth to a beautiful baby girl!

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