A cyst on the head of the fetus in the 5th month of pregnancy may be normal, but pathologic factors such as chromosomal abnormalities cannot be ruled out, which can be treated by temporary observation, chromosomal examination, and termination of pregnancy. During pregnancy, the choroidal villi within the fetal choroid plexus grow faster, and some cerebrospinal fluid can be wrapped within the choroidal villi, forming a cyst-like structure called choroid plexus cyst, which is usually normal. The ultrasound can be repeated after half a month to see the growth of the cyst. Most choroidal cysts disappear on their own. If the fetus has other malformations, there may be chromosomal abnormalities, and amniocentesis should be performed to detect malformations. If the malformations are more serious, the pregnancy can be terminated if necessary. If there is a cyst on the head of the fetus in the fifth month of pregnancy, it is recommended to consult a doctor in a timely manner, under the guidance of the doctor, improve the relevant examination, clarify the cause of the disease, and symptomatic treatment.