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The Nub Theory Boy Nub

Updated: May 8, 2021

Boy Nub Explained

All babies have a nub between their legs, this is called the genital tubercle. A genital tubercle or phallic tubercle is a body of tissue present in the development of the reproductive system. This is comprised of three areas, the genital tuber, urogenital fold, and the labioscrotal fold.

The fetal nub forms at the ventral, caudal region of both fetal sexes, and eventually develops into the primordial phallus. Until about 7 to 8 weeks of pregnancy both sexes will have a preliminary set of genitalia that will eventually develop to become either the male or female sex organs. This means, that both male and female genitalia start from the scene foundation.

For male fetuses, the genital tubercle will develop into the glands of the penis, the urogeneral fold becomes the shaft, and the labioscrotal fold matures into the scrotum.


Males can image differently.

Some will image with a forked shape nub and this forked nub tells us that the male is slightly under developed. They can sometimes show negative space directly underneath the nub and the tip may also look flicked or sloped at an upwards angle. We also see the classic boy nub, a short scrotal line with a bright white stack on top, this is the penis in development. Sometimes we can see just scrotal line image or scrotal line with a small hint of a shadow above the nub. Early boys can also be predicted from as early as 11.6 weeks in gestation, some boys are early developers and in this case show a clear scrotal line and penis in development.

See below our examples of how boys can image

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