33 weeks pregnant fetal posterior cranial fossa pool widening 1.2cm other cerebellum no problem, generally abnormal, posterior cranial fossa pool no longer continue to widen, the impact on the fetus should not be too big, first observation. The posterior cranial fossa is an important structure in the human cranium, this tissue structure contains the human cerebellar medulla oblongata pool, cerebellar tissue, posterior cranial fossa pool widening refers to the posterior cranial fossa this part of a large amount of fluid, from the ultrasonography will be found in the widening of the fluid plane, the widening of the posterior cranial fossa pool may be a physiological phenomenon, it may be a developmental abnormality of the fetus. Fetal widening of the posterior cranial fossa pool ≤ 1cm, normal cerebellar size and morphology, small posterior cranial fossa fluid, shrinking or no change during observation, generally has no effect on the fetus. The widening of the posterior cranial fossa pool in the 33rd week of pregnancy is within the range of 1.2cm, that is, 1-1.5cm, and it is necessary to closely observe the changes of the effusion, measure the size of the cerebellar hemispheres, check whether there is any abnormality in the structure of the fetal brain tissue and chromosomal problems, and review the ultrasound on a regular basis, and it will not be a big problem if it doesn’t continue to widen any more. If the fluid continues to widen in the later stages, hydrocephalus will affect the intelligence of the fetus. After pregnancy, do a good job of pregnancy and obstetric examination, abnormalities timely detection and treatment.