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All infants are at risk for adverse outcomes, but the risk is
far higher for infants that require neonatal intensive care. Many
of the highest risk infants require neonatal intensive care. Most
of the conditions that place a neonate at risk of dying (eg, preterm
birth, sepsis, organ injury or malformation) also increase the risk
of subsequent health and neurodevelopmental problems. Over the last
half century, major advances in high-risk obstetrics and neonatal
intensive care have yielded dramatic reductions in neonatal mortality
at all gestational ages.1,2 There has been no concomitant
dramatic reduction in frequency of health problems or neurodevelopmental
disabilities. Since no one can foresee the future for an individual
infant, prediction of outcome relies on assessment of the infant’s
current status (eg, neuroimaging and examination findings) as well as
prenatal, perinatal, and neonatal risk factors, illnesses, and treatments.3,4
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Maturation of the central nervous system (CNS) is a dynamic process.
Successive stages of neuromaturation have been described in the fetus,
preterm infant in a neonatal intensive care unit, preterm infant
at term, full-term neonate, infant, toddler, and child.5-7 Our
genome drives neuromaturation, but continuous gene-environmental
interactions make us who we are. Structural development of the central
nervous system is continuously modified by first the intrauterine, then
the extrauterine, environment. Just as fetal breathing
movements of amniotic fluid are necessary for lung development,
sensory input and fetal movement help shape the central nervous system.
Patterns of electrical activity associated with movement and sensory
input shape neural networks during synaptogenesis and later determine
which pathways are pruned.
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While most infants are born near term (ie, 40 weeks’ gestation),
with no major difficulties, and grow up without any impairments,
the challenge for prediction of outcomes is to recognize those processes
that alter or interfere with neuromaturation. The greater challenge
is to understand the mechanisms of unfavorable processes and to
develop strategies to prevent or promote recovery from them.
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We focus on risk factors because it is not possible to make a
diagnosis of neurodevelopmental disability in the neonatal period,
even with evidence of brain injury from neuroimaging studies.1,3,4 In
infants with birth weights below 1000 g and either intraparenchymal hemorrhage
or white matter injury on ultrasound, 28% to 30% had
no neurodevelopmental impairment at 18 to 22 months.8 Neurodevelopmental
diagnoses require assessment of neuromaturation with sequential attainment
of motor, cognitive, and adaptive skills during infancy and childhood.3,5 The major
disabilities (ie, cerebral palsy, intellectual disability) generally
can be diagnosed within the first 3 years, but learning disability, attention
deficit, and minor neuromotor dysfunction require follow-up to the
preschool and school years.3,9,10
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The absence of risk factors does not guarantee a normal outcome.
In the general population, 1% develop intellectual disability
and 0.1% to 0.4% develop intellectual disability
as shown in Table 62-1.3 Up
to ...