Fetal cerebellar medullary pool width of 1.1cm is serious or not needs to be judged according to the specific situation, this result may suggest the existence of cerebellar developmental abnormality, but further examination is needed. Generally speaking, the width of the medullary pool of the cerebellum should be less than 1cm, and at this time, the width is 1.1cm, which is relatively out of the range, this situation may be caused by physiological reasons, or it may be the emergence of a disease, which requires further examination to determine. If the result of further examination is not abnormal, it means that it is caused by physiological factors, which is usually not too serious, but should follow the doctor’s advice to carry out regular re-examination in order to exclude possible risks. This condition may also be caused by disease. If further examination reveals chromosomal abnormalities, posterior cranial fossa pool cysts, hydrocephalus, etc., the condition may be more serious, and the doctor will give diagnosis and treatment advice based on the results of the examination, and the pregnancy may have to be terminated if necessary. Women should undergo regular pregnancy checkups to monitor the health of the mother and the fetus at all times.