Some of the causes of fetal hydrocele are genetically related, but most of the causes are still related to hormonal disorders in the mother’s body during pregnancy. If the level of estrogen in the body is too high, it can cause separation of the collecting system, also called hydronephrosis. In fact, fetal hydronephrosis is found when the child is still in the mother’s womb, and it is usually described according to the amount of hydronephrosis, usually not more than 10 mm is described as separation of the collecting system of the kidney, and some ultrasound directly describes three to five mm as hydronephrosis.