Birth represents an
obligatory transition that disrupts fetal organization
and places new demands on the infant. For example,
at birth the newborn must make the transition
from fetal to neonatal circulation, initiate regular respirations, maintain thermoregulation, and
organize metabolic processes to achieve postnatal
homeostasis. After birth, the infant must reorganize
endogenous rhythms, physiologic functions, and
behavioral characteristics to respond appropriately
to the extranterine environment. The preterm infant
experiences greater difficulty in developing these
organizations owing to immaturity of the central
nervous system and other bodily systems, as well as
early environmental limitations relating to the
characteristics of the neonatal intensive care unit
environment.