Throughout the course of pregnancy, the fetus develops gradually in all systems and organs. Therefore, no factor causes abnormalities in the development of the fetus during pregnancy. Fetal hydrocephalus is a common condition during pregnancy and many pregnant women are found to have fetal hydrocephalus during prenatal checkups. Many pregnant women find fetal hydrocephalus during prenatal checkups and become overly worried because they do not understand the principles of fetal hydrocephalus. The causes of fetal hydrocephalus are divided into the following three categories: i. Excessive production of cerebrospinal fluid. Normal fetal brain tissue will produce cerebrospinal fluid on its own. However, the production and absorption of cerebrospinal fluid are in balance. If the production of cerebrospinal fluid is greater than the absorption of cerebrospinal fluid, then hydrocephalus will occur. This can occur in fetuses with intracranial tumors. But it is not common. Second, cerebrospinal fluid absorption is impaired. Fetal intracranial inflammation can lead to impaired absorption of cerebrospinal fluid, which can lead to hydrocephalus. Cerebrospinal fluid circulation disorder. Some fetuses can cause cerebrospinal fluid circulation disorders due to congenital factors, leading to hydrocephalus. Finally, it should be emphasized that most fetal hydrocephalus, if the diameter is less than 1cm, are not considered abnormal state. In summary, the causes of fetal hydrocephalus can be divided into: excessive cerebrospinal fluid production, impaired cerebrospinal fluid absorption, and impaired cerebrospinal fluid circulation.