Mucus inside the newborn’s undescended umbilical cord may be caused by umbilical cord infection, viral infection, foreign body irritation and other reasons. 1. Umbilical cord infection: it is the inflammation of the umbilical cord caused by Staphylococcus aureus, the inflammation of the cells and proteins and so on into the surface of the mucous membrane, which leads to the emergence of oozing, manifested in the umbilical cord and the skin around the umbilicus red and swollen, with abnormal secretions, such as mucus-like secretions and other manifestations. 2. viral infection: it is caused by the spread of viruses to infect the body, viral infection will lead to hypersecretion of cells, which will secrete mucus. 3. foreign object stimulation: may be clothes and other stimulation caused by foreign object stimulation will lead to local vascular tissue will have liquid exudation, there will be mucous secretion, will also be accompanied by the umbilical cord around the skin redness and swelling of the performance. Mucus inside the umbilical cord of a newborn can also be caused by eczema or by the fact that the umbilical cord has not yet fallen off. If the symptoms of mucus inside the umbilical cord of a newborn baby persist and do not resolve, it is necessary to give targeted treatment or therapy, under the supervision of a doctor.