An infant who falls on the back of the head usually needs to be observed for three days, or 72 hours. If there are no abnormalities within 72 hours of the injury, it is possible that the child is fine. Babies who fall on the back of the head may have no obvious symptoms, but may also experience mild drowsiness and vomiting, and in severe cases, projectile vomiting and convulsions. Under normal circumstances, infants will show abnormalities within 24 hours after the fall, or it may extend to 72 hours. If an infant has fallen over the back of the head and develops obvious abnormalities, such as drowsiness, vomiting and crying, he or she needs to go to the hospital in time and be treated under the guidance of a doctor. It is recommended to observe closely and seek medical attention promptly after the fall.