The exact time when hydrocephalus occurs in the fetus varies and is usually more common in the fourth to seventh month of pregnancy. Under normal circumstances, cerebrospinal fluid is produced and absorbed continuously in the skull in a state of dynamic equilibrium. If there is excessive production of cerebrospinal fluid or impaired absorption and reflux, a large amount of cerebrospinal fluid can accumulate in the ventricular system to form hydrocephalus. Fetal hydrocephalus belongs to a kind of neural tube defect disease, and its causes are complicated, which may be related to genetic factors, infectious factors, congenital embryonic dysplasia, inappropriate use of medication, genetic or chromosomal abnormalities and so on. If the ultrasound shows that the fetal head circumference is more than two standard deviations from normal or suggests widening of the ventricles, hydrocephalus may be considered, and there are individual differences in the time of onset of hydrocephalus, which may need to be examined by fetal cranial magnetic resonance imaging, except for whether there is a combination of other intracranial structural abnormalities. Once the diagnosis is confirmed, the next step in treatment should be decided in consultation with an obstetrician and a pediatric neurosurgeon. In addition, you should avoid the use of medication and prevent infections during pregnancy, take regular pregnancy checkups, do a good job of screening for abnormalities, avoid being overly nervous, and actively cooperate with your doctor’s guidance.