Small genitalia in children are mainly caused by the following reasons: 1. Malnutrition can cause growth retardation, resulting in small genitalia. 2. When suffering from cryptorchidism, the genitalia are hidden in the fat of the penis and prepubic bone, making the spongy part of the penis buried in the subcutaneous tissue, which looks smaller than children of the same age from the outside. 3. 5. When suffering from congenital endocrine disorders, it can lead to short genital appearance. In short, all of the above causes can cause genital shortening.