A few days after the umbilical cord of the newborn is detached and then suddenly bleeding may be caused by the trauma is not completely repaired, umbilical cord inflammation, vitamin K deficiency and other reasons. 1. The wound is not completely repaired: a little bleeding after the umbilical cord of a newborn is not completely repaired after the umbilical cord is detached, the local granulation tissue proliferation and other reasons for bleeding, generally less bleeding, pay attention to wound care and observation, the wound will slowly heal. 2. Umbilical cord infection: After the umbilical cord is detached, the capillaries of the umbilical granulation tissue seep blood, which is easy to be infected, and there will be purulent secretion or bleeding after the umbilical cord infection is triggered. 3. Vitamin K deficiency: the umbilical cord oozing more blood, bleeding more, may be the umbilical cord after detachment of late-onset, late-onset vitamin K deficiency, to go to the hospital to check the blood routine, coagulation function. Newborns who have bleeding again a few days after the umbilical cord is detached are advised to seek prompt medical treatment.