Pregnancy is an incredibly developmental and trying time in every couple’s life. With all of the mood swings, hormones, and cravings, this period is stressful for all involved.

However, it all becomes worth it when you finally learn the gender of your child and can begin preparing for the incredible journey ahead.

When it comes to pregnancy, gender can be a very nuanced subject. Some parents are desperate to know what their child will be, while others go out of their way to avoid it. The majority of parents, however, belong to the former category.

In fact, many parents will begin to search for clues of their little one’s gender as early as their 12-week scan, becoming more desperate to know the more time goes on.

Thanks to a lesser-known phenomenon known as the Nub Theory, however, guessing may no longer be a part of the equation.

What is Nub Theory?

Nub Theory is a lesser-known gender prediction method used to determine a baby’s sex as early as twelve weeks. This theory operates on the scientific basis that your child’s genital nub, or genital tubercle, that will eventually become a clitoris or penis can reveal your child’s sex before the genitals even begin to take shape.

According to recent studies, this method has proven to be 100 percent accurate at as early as 13 weeks. At twelve weeks, the theory is still a precise determiner, as the accuracy percentage is shown to lie at about 91.5 percent.

This is because the angle of the tubercle is increasingly gender-specific the further along you are. In essence, if the tubercle angle at 12-14 weeks is less than thirty degrees, the baby is likely a girl. If it is greater than thirty degrees, the child is likely a boy.

Nub Theory
Boy usually creates an angle exceeding 30 degrees in relation to the spine, while girl produces at the same direction and below 30 degrees in relation to the spine.

Most of the error percentage in this practice comes from the development timeline of the genital nub. If you were to attempt this too early in the pregnancy, the result would be inaccurate due to the tubercle being too far underdeveloped.

Who invented Nub Theory?

Nub Theory was first brought to the public eye by Becky Taylor, who stated that nub theory could help in finding the sex of the baby through a tiny bud. Over time, this enticing medical procedure gained popularity and was picked up on several health and pregnancy blogs worldwide.

Today, Nub Theory is still a controversial issue, as its validity has not yet been wholly proven within the medical community. This means that, while it is not routinely performed, parents can still request a gender determination using Nub Theory at their twelve-week prenatal scan.

Scientific proof of Nub Theory

Despite Nub Theory’s controversial nature within the medical and scientific community, there are studies that back up its validity. A primary example of this is a medical research study performed in early 20121 which aimed to determine the new theory’s relative accuracy and reliability.

Overall, the research spanned 1,222 cases. This study also found that this theory’s accuracy was based less on the overall age of gestation but much more on the baby’s size in question. For example, a smaller baby, further along, could be less accurate than a larger baby of the same gestational age.

The results of this research determined indicated it was possible to reliably determine a baby’s sex as early as 12-14 weeks with an accuracy of 96.6 to 100 percent, with most of the variation influenced by smaller, less developed babies.

While the percentage of accuracy and positive results determined by nub theory is high, the procedure is not a simple one. For this method to be as reliable as possible, the sonographer must be able to adjust the baby’s position. This is because the so-called “angle of the dangle” is determined in relation to the baby’s spine, which needs to be relatively straight as compared to the pelvis.

For this reason and many more, the Nub Theory has not yet made its debut into standard medical practice.

Final Verdict

Overall, nub theory is an accurate, albeit challenging, method of providing sex determination to impatient parents that can’t wait any longer.

Accurate at as early as twelve weeks, this theory has not yet found a solid foundation for common medical practice but still undoubtedly remains backed by numerous research studies and reliable medical practicians.

Without a doubt, this theory will continue to grow in popularity as time advances, but for now, it will remain more a fun hint at what you could be having rather than a solid determination.


  1. Lubusky M, Studnickova M, Skrivanek A, Vomackova K, Prochazka M. Ultrasound evaluation of fetal gender at 12–14 weeksBiomed Pap Med Fac Univ Palacky Olomouc Czech Repub. 2012;156(4):324–329.