The disease is divided into three types: early, classic and late, and the late type is also called late. They are described below. The bleeding can be mild or severe, and in mild cases, it is only a small amount of skin bleeding, blood leakage from the umbilical cord stump, cranial hematoma, while in severe cases, there can be a large amount of gastrointestinal bleeding, manifested as vomiting blood, black stool or fresh blood in the stool; there can also be severe intracranial bleeding, chest or abdominal bleeding. The occurrence is related to the mother’s use of drugs that affect vitamin K metabolism before delivery. However, severe neonatal hemorrhage is rare clinically. 2. Classic: Bleeding occurs 1-7 days after birth, with most onset on the second to third day after birth. It may manifest as blood leakage from the umbilical cord stump and gastrointestinal bleeding. Gastrointestinal bleeding is manifested as vomiting blood or blood in the stool; there can also be bleeding from skin pressure, puncture sites, vaginal bleeding, nasal bleeding and pulmonary bleeding. Most children do not bleed much and stop on their own. However, there are a few children with severe bleeding, including large skin petechiae and hematomas, massive bleeding from the gastrointestinal tract or umbilical stump, and adrenal cortical bleeding that can lead to shock. Intracranial hemorrhage mostly occurs in premature infants and can be severe enough to lead to death, while those who survive may have sequelae such as hydrocephalus. The occurrence of this type is related to exclusive breastfeeding, intestinal flora disorders, and insufficient vitamin K synthesis due to liver underdevelopment. 3.Late onset: (Late onset) refers to neonatal hemorrhage that occurs after 8 days of life. It occurs mostly from 2 weeks to 2 months after birth and is mostly characterized by sudden intracranial hemorrhage. Intracranial hemorrhage can be subdural hemorrhage, subarachnoid hemorrhage, epidural hemorrhage, clinically manifested as convulsions, commonly known as convulsions, accompanied by vomiting, bulging fontanelle and other symptoms of increased intracranial pressure, and can also be accompanied by bleeding from other sites, such as skin, injection sites, gastrointestinal tract and submucosa. Intracranial hemorrhage is often large enough to compress the surrounding nerves causing brain cell necrosis or leading to hydrocephalus. Severe hemorrhage often leads to death, and those who survive are often left with neurological sequelae. These include developmental delays, motor dysfunction, cerebral palsy, and epilepsy, causing a great burden to the family and society. The disease occurs mainly in infants who are exclusively breastfed and have not been supplemented with vitamin K since birth. It can also occur secondary to infants with hepatobiliary disease, chronic diarrhea and long-term antibiotic use.