It is possible that the widening of the posterior cranial fossa pool at 37 weeks can be self-absorbed, so it is recommended to observe the baby for a few days before undergoing an ultrasound. Whether the widening of the posterior fossa pool can be self-absorbed depends on whether the posterior fossa pool of the fetus will continue to widen in the later stage. If it will not continue to widen, it is generally safe and can be self-absorbed, and will not affect the health of the fetus. The fetal posterior fossa pool is usually less than 10mm, and once it exceeds 10mm, it is a widening of the posterior fossa pool. Some normal fetuses may also have widening of the posterior fossa, which generally does not affect fetal growth and development. If the pool of the posterior fossa continues to widen, it suggests that the fetus may have hydrocephalus or malformations, and needs to be taken seriously. Pregnant women are advised to undergo active obstetrical examination, and according to the results of the obstetrical examination, active treatment under the guidance of specialists is required.