Neonatology is a subspecialty of pediatrics that consists of the medical care of newborn infants, especially the ill or premature newborn. It is a hospital-based specialty, and is usually practiced in neonatal intensive care units (NICUs). The principal patients of neonatologists are newborn infants who are ill or require special medical care due to prematurity, low birth weight, intrauterine growth restriction, congenital malformations (birth defects), sepsis, pulmonary hypoplasia or birth asphyxia. While high infant mortality rates were recognized by the British medical community at least as early as the 1860s, modern neonatal intensive care is a relatively recent advance. In 1898 Dr. Joseph DeLee established the first premature infant incubator station in Chicago, Illinois. The first American textbook on prematurity was published in 1922. In 1952 Dr. Virginia Apgar described the Apgar score scoring system as a means of evaluating a newborn's condition.
It was not until 1965 that the first American newborn intensive care unit (NICU) was opened in New Haven, Connecticut. In 1975 the American Board of Pediatrics established sub-board certification for neonatology. The 1950s brought a rapid escalation in neonatal services with the advent of mechanical ventilation of the newborn. This allowed for survival of smaller and smaller newborns. In the 1980s, the development of pulmonary surfactant replacement therapy further improved survival of extremely premature infants and decreased chronic lung disease, one of the complications of mechanical ventilation, among less severely premature infants. In 2006 newborns as small as 450 grams and as early as 22 weeks gestation has a chance of survival. In modern NICUs, infants weighing more than 1000 grams and born after 27 weeks gestation have an approximately 90% chance of survival and the majority have normal neurological development.