The body size differences are paralleled by maturation changes. The smaller body of an infant or neonate is substantially different physiologically from that of an adult. Congenital defects, genetic variance, and developmental issues are of greater concern to pediatricians than they often are to adult physicians.
A common adage is that children are not simply « little adults ». The clinician must take into account the immature physiology of the infant or child when considering symptoms, prescribing medications, and diagnosing illnesses.
A major difference between the practice of pediatric and adult medicine is that children, in most jurisdictions and with certain exceptions, cannot make decisions for themselves. The issues of guardianship, privacy, legal responsibility and informed consent must always be considered in every pediatric procedure. Pediatricians often have to treat the parents and sometimes, the family, rather than just the child. Adolescents are in their own legal class, having rights to their own health care decisions in certain circumstances. The concept of legal consent combined with the non-legal consent (assent) of the child when considering treatment options, especially in the face of conditions with poor prognosis or complicated and painful procedures/surgeries, means the pediatrician must take in to account the desires of many people, not just the patient.
The first generally accepted pediatric hospital is the Hôpital des Enfants Malades, which opened in Paris in June 1802 on the site of a previous orphanage.
Pediatricians must undertake further training in their chosen field. This may take from four to eleven or more years, (depending on jurisdiction and the degree of specialization). The post-graduate training for a primary care physician, including primary care pediatricians, is generally not as lengthy as for a hospital-based medical specialist.
In the United States, a medical school graduate wishing to specialize in pediatrics must undergo a three-year residency composed of outpatient, inpatient, surgical, and critical care rotations. Specialties within pediatrics require further training in the form of 2-3 year fellowships. Specialties include critical care, gastroenterology, neurology, infectious disease, hematology/oncology, rheumatology, pulmonology, emergency medicine, endocrinology, neonatology, and others.