All nubs will image as a fork. The fork is split into two parts. The bottom half, also known as the urogenital folds will develop into the labia minora, and the top half known as the genital tubercle will develop into the clitoris. By 11 weeks of gestation, the clitoris is prominent and the lateral boundaries of the urogenital sulcus have separated.  For male fetus the genital tubercle will develop into the glans of the penis, the urogenital fold becomes the shaft and the labioscrotal fold matures into the scrotum. At your NHS dating scan at around 12 weeks, your sonographer will be able to capture a clear shot of your baby's nub, (if they are a believer in the nub theory) if not you can ask for a side profile shot of your baby, this will most likely show their nub.If your baby is showing a clear nub shot, the accuracy of your prediction will be extremely high, up to 99.9%. It is rare for a nub theory prediction to be incorrect by our team, especially if a fully imaged nub has been captured. If this does happen, its usually when the baby's gestation is early, if at around 12-12.2 weeks, his nub may have presented parallel, this means his genitals may have taken a little later to develop (a late riser).



The nub theory is  proven to be the most accurate form of early gender prediction today. Now backed by science. The nub theory is one of the most talked about theories across the internet, when it comes to pregnancy. However, unfortunately some will still argue that the nub theory is just a myth or 50:50. This is simply not true. Depending on who is analysing your scans and the experience they have, will ultimately lead to the prediction being correctly identified or not. For example, most companies will see a "stacked nub" and instantly predict that the baby will be male, however the angle plays a huge part in this analysis and if the nub appears stacked but the angle is parallel then the baby is female. (stacking does not mean boy!)

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A nub is your baby's genitals in development. The genital tubercle bump (nub) will start to develop from around 8 weeks in gestation, this can be seen via ultrasound from as early as 9 weeks. However, accurately assessing your baby's nub is not reliable enough until the 12th week. All babies will have  a nub between their legs, the angle of the nub, will indicate whether your baby is a boy or a girl. If your baby's tubercle is pointing at a caudal angle (downwards towards the rump) and less than 30 degrees to the axis of the dorsal surface (baby's back/spine), this would indicate your baby is  female. If the tubercle is at a cranial angle (upwards towards the cranium) and at an angle greater than 30 degrees to the axis of the dorsal surface, this indicates your baby is male.

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The developing female nub varies at different gestations, the nub here is parallel to her spine, it also sits below 30 degrees and you will also find her nub hangs directly off her rump.


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We often get asked, if a nub is showing as a fork it has to be a girl, is this right? This information is actually incorrect. The length and shape of your baby's nub may sometimes indicate gender, but not always.For example, some say that a “forked nub” is indicative of a girl fetus, however we do not adopt this, as its clear that both sexes can be seen with a forked nub in the early stages of development.  The reason you see a fork shaped nub in both female and male fetuses, is because this fork serves an important purpose. For females, this fork will become the labia and clitoris, for males, the top half of the fork will develop into the penis, and bottom fork into the scrotum.We also know a forked nub is a sign of an undeveloped nub or a late riser (in males)



We know that all baby's are different and so is their development rate in the womb. Some male baby's in the 11th to the early 12th week can develop more rapidly than others, the term "early boy" is used to describe this. At the end of the 11th week going into the beginning of the 12th week most nubs will image parallel and the term used for this is "early girl".  From 12.5 weeks to 13 weeks (a matter of a few days) a nub can image parallel, but develop that little bit later and be confirmed boy, this happens in around 6% of  baby's and the term used is "late riser".


When analysing your baby's nub there is much more that goes into it than just the than just the angle. We take into account your baby's gestational age, this being the most important factor, bladder position, this helps us identify the correct angle in which your nub points too. Your baby's spine, if this is curved or straight, depending on how your baby has imaged in the womb during scanning. The appearance of your baby's nub, they can image in several ways, your baby's legs (the positioning) if and where they are located and so much more.


When we draw your baby's nub, we  draw each one individually, we start at your baby's face, then the body, the nub and then all the extras like cord and leg that image too. Visually we try and give you a real life view of exactly how baby was captured during scanning. We have been asked on occasion if a computer draws your baby, the answer to this is absolutely not. We have added a video below to show you how we work. 


Real life view of a baby's nub. The top image is of a baby girl, her urethral opening down the middle stays open this means she will be a female and the bottom image is of a baby boy, his urethral groove closes and this means he will develop into a male.

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The information provided to you is backed by many years of knowledge on the nub theory. We are not medical professionals nor do we provide medical advice.

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