The causes of newborns’ buttocks green are Mongolian spots, trauma and so on. 1. Mongolian spots: a relatively common birthmark, mostly in the newborn’s waist, buttocks, sacrococcygeal tail gray-blue or dark blue, round, oval-shaped plaque, the border is not too clear, nor above the surface of the skin, touch and normal skin as smooth. Generally and hereditary related, also do not need treatment, will slowly subside with the growth of the newborn. 2. Trauma: new parents do not take good care of their newborns, resulting in the newborn’s buttocks by the hard object of the bump, the symptoms of bruising. When parents touch, the newborn cries due to pain. Remind parents, careful care of newborns, found that the buttocks green to find the cause, if necessary, seek medical attention to identify the cause of the disease.