Can You Predict Baby’s Sex Using Nub Theory?

4 min read

Written by Aparna Hari

Aparna Hari

Her experience in impactful writing combined with her background in Home Sciences makes Aparna the perfect candidate for content writing in the pregnancy and parenting niche.

Predict Baby`s Sex Using Nub Theory

If you are pregnant, you would be quite curious to know the sex of the baby. Especially if you are between 18 to 22 weeks of pregnancy, the upcoming anatomy scan can give you a lot of exciting information, including the sex of the baby. So can you predict a baby’s sex using nub theory?

In this article, we shall discuss more what nub theory is, how it works, how it helps predict the sex of the baby, and the accuracy of the theory.

In This Article

What is Nub Theory?

A Genital Tubercle forms in the baby’s lower abdomen during early pregnancy, and this turns into a tubercle, also known as a “Nub.” The Nub eventually turns into a penis or Clitoris in male or female babies.

How Does Nub Theory Work?

How does nub theory work

During the 8th to 9th week of pregnancy, the genital tubercle starts growing and taking form. But the shapes look very similar until the 14 weeks. But, the 12th-week ultrasound helps to predict the further growth of the tubercle.

The Nub theory explains that if you can get a good look at the nub, you can determine how it will grow out in the upcoming ways. The angle of the nub in connection with the spinal cord can help you determine if the nub will grow out into a penis or Clitoris.

Can You Predict the Sex of The Baby Using Nub Theory?

Yes. You can predict the sex of the baby using the Nub Theory. For this, you need to find a clear picture of the nub to make the spine visible horizontally. You can check the nub or any small protrusion where your baby`s legs will form horizontal vision.

If your baby’s nub is inclined at 30 degrees to its spine, it indicates that you will have a boy baby. But how will someone measure the 30 degrees? To determine this, take your ultrasound and draw a straight line along the spine or where the butt is; you can identify the direction of the nub.

If the nub is pointing up away from the straight line, it is a boy. If the nub is pointing downwards, it indicates a girl.

How Accurate is the Nub Theory?

Nub Theory is an excellent way of determining the sex of the baby. But there is not much evidence behind the theory. The internet has a lot of information on the Nub Theory, and some sites might say that the prediction is hundred per cent accurate.

Though there is no evidence backing up the theory, this is not a made-up one. Older studies have proven that the sex of the baby can be determined from the early ultrasound depending on the angle of the genital tubercle.

A study was conducted in 1999, where the researchers studied the ultrasound of babies who were 11 to 13 weeks of gestational age. They concluded that, during the 11th week, the accuracy level was 70 per cent, whereas, in the 13th week, accuracy moved to 98 per cent.

A similar result was also observed in a subsequent study conducted in 2006 with a larger sample size.

However, in 2012, a further study was conducted with expanded sample size. The accuracy was much lower in the initial weeks and improved as the gestational age increased. Thus, the higher the gestational age, the more accurate the results of Nub Theory would be.


1. Can You See a Nub at 10 Weeks?

Yes. You can see a Nub or tubercle between the 8th to 9th week, where it begins to take shape. But, the clarity of the shape and the direction of the nub can be sought only after 14 weeks. The 12th-week ultrasound can give you an idea about the direction of the Nub growth.

2. Can You Tell Gender by Nub?

Yes. The angle of incidence of the nub between the spine of the baby determines the gender of the baby. If the angle of the nub to the spine is 30 degrees, you will have a boy baby. If the angle of incidence is pointing downwards from the 30 degrees, you will have a girl baby.

3. How Accurate is the Nub Test at 12 Weeks?

The studies have proven that the accuracy level of the nub theory at 12 weeks is 85 per cent compared to 70 per cent in the 11th week. It is believed that as the gestational age increases, the accuracy levels increase. During the 13th week, the accuracy level increases to 97 per cent. The mischaracterization of a baby boy as a girl and vice-versa is very common.

Read Also: Chinese Gender Predictor : Guess the Gender of your Baby

Aparna Hari,MBA in Marketing,P.G. Diploma in Human Resource Management from IGNOU Bachelor of Sciences (Home Science) from Nagarjuna University

Her experience in impactful writing combined with her background in Home Sciences makes Aparna the perfect candidate for content writing in the pregnancy and parenting niche.Read more.

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