Rib ectropion may be a normal physiologic developmental process, or it may be caused by a simple malformation of the rib cage. Rib ectropion refers to the phenomenon that the lowest edge of the rib cage exceeds the outer edge of the body. Rib ectropion is caused by the fact that the two lowest ribs of the human sternum are not directly connected to the sternum, and that infants will have rib ectropion when they breathe with a large amplitude of abdominal movement and have a softer rib cage, which will be close to that of an adult as they develop. Rib ectropion can also be caused by trauma or prolonged squeezing of the ribs during the growth process, which affects the child’s development and results in deformed development. If rib ectropion occurs and affects the child psychologically, timely medical treatment is needed.