The widening of the fetal lateral ventricles needs to be analyzed and judged according to the exact degree of widening. If the widening is within 10mm, it is mostly physiological, between 10-15mm is suspected hydrocephalus, and 15mm and above is hydrocephalus. The main causes of pathological widening of the fetal lateral ventricles include: 1, specific pathogenic microbial infections during pregnancy, such as cytomegalovirus infection, toxoplasma infection, syphilis infection, etc., which affect the development of the central nervous system; 2, chromosomal abnormalities, resulting in abnormal development of the fetal central nervous system, etc.; 3, nutrient deficiency causing abnormal development of the central nervous system, such as neural tube malformation caused by folic acid deficiency; 4, no exact cause of the widening of the fetal lateral ventricles; 4, abnormal development of brain structures without exact cause, resulting in impaired cerebrospinal fluid circulation.