Nub theory explained: Predict your baby's sex at 12 weeks

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Nub theory
Can you tell if your baby is a boy or girl from just 12 weeks? We've all heard of the old wives tales like carrying your baby bump low means it's a boy or if you're craving sweet things, you're expecting a girl.

But have you heard of the nub theory? If you're looking for the nub theory explained, or want some more ideas on how to tell your little one's gender, you've come to the right place.

The nub theory claims to be a lot more accurate than some of those old wives tales - and says you can even tell the sex of your baby just by looking at your 12 week ultrasound picture. Usually the earliest point you can tell the sex of a baby from a scan is 20 weeks so the quirky theory is popular with those who can't wait to find out if they're having a little girl or a little boy.

What is nub theory?

Between 11-13 weeks, all babies are said to have a 'nub' between their legs called the genital tubercle, and according to this theory the angle of the nub will indicate whether it's a boy or girl.

It's said that if the nub is over 30 degrees up from the spine, it's a boy - but if it's under that then it's a girl.

Confused? See our pictures below as an example.

Nub theory indicating a girl

Nub theory - girl picture
The nub isn't pointing up more than 30 degrees from the baby's spine - in fact it's almost horizontal - so believers would say this showed the scan to be a little girl.

Nub theory indicating a boy

Nub theory - boy picture
The nub is at a much steeper angle upwards from the spine, indicating that this could be a baby boy.

Not convinced? Netmums have reported the following statistics inline with the nub theory:

  • At 11 weeks, the accuracy rate is 48 per cent

  • At 12 weeks, the accuracy rate is 91 per cent

  • At 13 weeks, the accuracy rate is 94 per cent

  • Going for your scan soon? You'll have to hope for co-operation from your baby as some professionals say the accuracy actually all depends on the angle of the baby. If you can get a picture of them laying down on their side, that should provide you with a good view of the nub.

    Continued below...

    If you had success using the nub theory then we'd love to know! Leave us a comment below or send us a message on ourFacebook page.

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    • 3
    (78 ratings)

    Your comments

    sherrell austin

    any guesses on this scan gender? Xx

    Michelle le Roux

    Any guess es boy or girl?


    Girl? =)


    Boy/ =)


    Still an embryo


    Boy =) let me know?

    Kira Sturrs

    boy or girl

    Kira Sturrs

    boy or girl 12 + 3 days please

    sandra cook

    Does it looks like a boy or girl


    Can any one guess the gender


    Can anyone tell me what they think the gender is? And what theory. 13 weeks


    Can anyone tell me what they think the gender is? And what theory. 13 weeks


    12 weeks 3 days boy or girl


    Hi everyone, This is my 12 week scan, could everyone please have a guess as to what you think it might be? Thanks!


    Girl or boy




    Any guesses


    Can someone help me boy or girl

    Sandeep Deokate

    Any Guesses on below gender is Boy of Girl ??

    Lorraine Ness

    Boy or girl

    Lorraine Ness

    Hey can anyone tell if it's a boy or girl


    Would you say boy or girl please? İ am 12+0 week.


    Boy or girl? Any guesses pls?

    Adam Smithson

    Boy or girl please


    Any ideas ???

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