It is not normal for a newborn to have a concave lower lip, and there are many reasons for this, such as daily habits and genetic factors. 1. daily habits: due to the bad habit of sucking milk, resulting in this situation, will gradually return to normal with the age of the child, usually pay more attention to the child’s growth and development. 2. Genetic factors: it may be due to the genetic situation of the parents to cause the fetus to appear this phenomenon, due to the maxillary bone forward protruding, so that the upper lip is located in front of the lower lip, appears to be the upper lip protruding and thus the formation of the lower lip to the concave, you can grow up some of the orthodontic treatment, wearing orthodontic appliances, such as fixed orthodontic appliances, functional orthodontic appliances and so on, you can gradually change this situation. It is recommended that newborns with concave lower lips should be diagnosed as soon as possible, and targeted treatment should be carried out as soon as possible.