A children's hospital (CH)[2] is a hospital that offers its services exclusively to infants, children, adolescents, and young adults from birth up to until age 18, and through age 21 and older in the United States.[3] In certain special cases, they may also treat adults.[4][5] The number of children's hospitals proliferated in the 20th century, as pediatric medical and surgical specialties separated from internal medicine and adult surgical specialties.