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Fetal Medicine - Scans Blog - Male fetus at 12 weeks

What is the Nub Theory?

All About Gender Scans with Dr Penman, Consultant Fetal Medicine Specialist in Kent

Knowing if your little one is a boy or girl is a burning question for many expectant mums and their families. Whether you’re a first-time or seasoned parent, whether the new addition to the family will be a boy or girl is an important factor in planning for their arrival.

With Dr Penman, you can know the gender with 80% accuracy from 12 weeks and with 99.9% accuracy from 16 weeks. Dr Penman uses his 25+ years’ experience as well as state-of-the-art scanning technology to give you these assessments.

In your search for information on gender prediction, you will probably have come across the nub theory. This is a theory that uses the angles of the genital tubercle (the ‘nub’) to tell if you’re expecting a boy or girl. In this article, we’ll explain more about the nub, how accurate it is and how soon you can have your baby gender scan. We’ll cover the following topics:

Only have 1 minute? Here's 5 takeaways about the nub theory

What is the Nub Theory?

The nub theory is one of many gender theories. It looks at the genital tubercle (the ‘nub’) to determine if baby is a boy or girl. It’s not a predictor, however, and can be wrong.

The theory is: the angle of the ‘nub’ in relation to the spine tells if it’s a boy or girl.

A boy has a ‘nub’ that’s angled more than 30° degrees in relation to the spine. Here’s what that looks like in an image.

Fetal Medicine - Blog - male fetus 12 weeks old

A girl has a ‘nub’ that’s angled less than 30° degrees in relation to the spine. Here’s what that looks like in an image

Fetal Medicine - Blog - female fetus at 12 weeks

How accurate is the Nub Theory?

It is, after all, just a theory. It’s not proven. That’s important to remember when looking at your scan photos at home.

Many studies suggest this theory may be accurate but don’t buy all pink or all blue just yet! It’s best to wait until you’ve had confirmation from your trained specialist, such as Dr Penman.

Dr Penman can assess baby’s sex via gender scan with 80% accuracy from 12 weeks and with 99.9% accuracy from 16 weeks. Book a baby gender scan in Kent with Dr Penman here. 

Alternatively, you can have a Harmony Test with Gender at 10 weeks. This test is 99% accurate at detecting gender at 10 weeks. However, Dr Penman does not recommend having this test solely for the purpose of knowing gender. The test is usually for prenatal screening for various chromosomal conditions such as Downs syndrome. Find out more about the Harmony Test here.

How early can Dr. Penman tell the gender of my baby?

With Dr Penman, you can know gender with 80% accuracy from 12 weeks and with 99.9% accuracy from 16 weeks. Dr Penman uses his 25+ years’ experience as well as state-of-the-art scanning technology to give you these assessments.

What affects the quality of my baby scan images?

Dr. Penman always tries his best to get you the great scan images that you’re after. He knows it’s important to you to see your baby before they’re born and have great images of them to remember for years to come.

There are, however, some things that can affect the quality of the images you get. Here are a few of them:

  • Baby’s position
  • Number of babies
  • Maternal BMI

Sometimes, your little one just isn’t in the right position to get the best scan images possible, or they’re too cramped next to their siblings if you’re expecting multiples. Often, if the mother has a raised BMI, this can decrease scan image quality too.

But, rest assured, Dr. Penman will make sure he tries his utmost to get you the best ultrasound images he can.