The fetus is still in the rapid growth period, and the development of fetal brain is sometimes faster than that of aqueduct system in the brain. When the amount of cerebrospinal fluid produced in the brain is obviously greater than the circulation capacity of aqueduct system, there will be a slight expansion of ventricular system, but this slight expansion will gradually disappear with the development of aqueduct system in the brain. When hydrocephalus is obvious, one side or all of the brain is often filled with fluid. I suggest that you don't be too nervous, check again after one month, and check again in time if there is any abnormality.