The Skull Theory

Skull Theory for baby gender prediction?

This theory is based on the study of the anatomy of the human skeleton. The study of the bones gives us a lot of information about the characteristics of the human being; analyzing them we can know the age, sex and even the race of a person. Knowing how much detailed information we can draw from bone structures, we believe it also serves to predict the sex of the baby because although the fetus is very small, one of the first things we can see in the ultrasound is the shape of his head, even when the body still doesn’t have a well-defined shape.

Therefore, this theory is based on the shape of the bones of the skull and the differences between the female and male skull, to determine the sex of the baby. Because no medical studies have been done on the relationship of the shape of a baby’s skull as in pertains to the gender, we can only rely on the online information provided in several sources that believe skull theory to be up to 92% accurate. We do however believe it is a great tool to help make a correct gender prediction.

How does the Skull Theory work?

For skull or cranial theory to be accurate you have to look at a series of key points in the skull of the fetus. Each of these markers will indicate if the bone structure is more similar to that of an adult male or female. There are several markers and different parts of the skull that need to be studied, if we are to draw an accurate gender prediction out of the skull we need to consider an exhaustive study of all the bone markers visible via diagnostic imaging.

The markers available for analysis at an early age are the following, however not all of them can be properly appreciated in a still image or ultrasound.
a) The female skull is more rounded than the male. If the top has a very rounded shape, it would be a girl. If it is flatter or square, a boy.

b) The temporal crest. The temporal crest is the one that runs along the outside of the skull. In men it is more prominent and has a more square shape and if it is practically not noticed it will indicate that it is a girl.

c) The space above the eyes. If the bulge just above the eyes is pointed indicates girl but if it is rounded, it would be a boy.

d) The superciliary arch. It is the one that forms under the lower eye socket and is larger and much more pronounced when the baby is a boy. On the contrary if it is small and little pronounced it would be a girl.

e) The jaw. The girls have a more rounded jaw while the boys tend to have a square and a little protruding.

f) The bone structure of the forehead. The girls have the part of the forehead, straight. In the case of children it is curved and more marked.

g) The cranial form as a whole. In the case of boys, the skull looks wider and the women narrower.

h) The shape of the gonion. The gonion is the point at which the jaw forms an angle and in children it is more marked and closed than in girls.

What does it all mean?

We understand that it might be difficult to understand what some of the points above mean, so we have written some examples in our own words.
If you are looking at an ultrasound image of your baby’s skull in a profile view, you will be able to see the outline of their skull. Here are the main things to look for if trying to determine the gender of your baby:


Male forheads tend to come out further than the silhouette of the nose.
Female foreheads tend to go straight from the nose until the hairline without protruding outwards.

Top of the head

Male head circumferences is usually larger and with more sharp angles.
Female head circumference might be smaller and with smooth, round edges.


Male tend to have a more outward and sharp edge chin.
Female tend to have a round and small chin.

The structure of the human skull is not a common topic of discussion; hence we get a lot of questions about the reliability of the skull theory when it comes to predicting the gender of a baby. Our answer to these questions is simple, it solely depends on the quality of the ultrasound, and it is greatly influenced by the gestational week it is being studied. As the fetus grows, bone structures get stronger and more solid, but even after birth baby’s skulls are moldable. This means that seeing a very masculine cranial structure at 12 weeks of gestation can still turn our to be a female baby in future gender determination. Because accuracy rates are yet to be determined -beyond the popular opinion of up to 92%- we believe the best way to use skull theory to achieve an accurate, early gender prediction is to use it in combination with the Ramzi theory or the Nub theory. By combining all the visible gender markings you enhance the visual reports and increase changes of accuracy.

When applying the skull theory to an ultrasound that shows a prominent nub or adding to a very high quality Ramzi theory ultrasound, the accuracy of the gender prediction by skull is greatly increased. When we already have a good idea that there are more markers of one specific gender, the skull structure and details can help us tremendously raise our accuracy rate and provides us and the pregnant mother with unique insight about the gender markers that can be seen at such an early stage in pregnancy. Many are able to see those gender markers develop into their baby’s looks and individual characteristics as time goes on.