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SECTION IV Consequences of Preterm Birth: 10 Mortality and Acute Complications in Preterm Infants
Pages 311-345

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From page 313...
... Few studies have reported mortality and morbidity rates in gestational age-specific categories, which limits the information available for counseling of parents before a preterm delivery and for making important decisions on the timing and the mode of preterm delivery. Although much progress in the treatment of infants born preterm has been made, many of the medications and treatment strategies used in the neonatal intensive care unit have not been adequately evaluated for their efficacies and safety.
From page 314...
... The risk of acute neonatal illness decreases with gestational age, reflecting the fragility and immaturity of the brain, lungs, immune system, kidneys, skin, eyes, and gastrointestinal system. In general, more immature preterm infants require more life support.
From page 315...
... . Dramatic declines in infant and neonatal mortality and gestational-age specific mortality over the last several decades have been attributed to improvements in obstetric and neonatal intensive care, especially for infants born preterm and small for gestational age (Allen et al., 2000; Alexander and Slay, 2002)
From page 316...
... have been developed. As the proportion of infants with birth weights of less than 1,000 grams born at Level III perinatal centers has increased, their survival has improved, and the gap in survival between infants born in and out of such centers has increased (Saigal et al., 1989)
From page 317...
... The role that defining and treating the complications resulting from preterm birth plays in the health and neurodevelopmental outcomes of children born preterm argues for more long-term outcome studies and more rigorous studies of new therapies and medications before they are widely adopted. Lungs and Respiratory System The primary function of the lung is gas exchange (i.e., they inhale oxygen and exhale carbon dioxide)
From page 318...
... The incidence of RDS increases with decreasing gestational age and is higher among white infants than African American infants at each week of gestation (Hulsey et al., 1993)
From page 319...
... Especially for infants born at less than 28 to 30 weeks of gestation, the lung tissue is very fragile and the injured lung tissue tends to trap air, collapse, or fill with mucus and other fluids, which further compromise lung growth and development. Various definitions of BPD/CLD have been used and are based on the respiratory support that an infant requires, but the most commonly used definition is a requirement for oxygen at 36 weeks of postmenstrual age (gestational age plus chronological age)
From page 320...
... . Two studies in the 1980s reported that long courses of relatively high doses of corticosteroids reduced the duration of time that oxygen and mechanical ventilation were needed in preterm infants (Avery et al., 1985; Mammel et al., 1983)
From page 321...
... . Immaturity of the control of breathing is the major cause of apnea and bradycardia, although sometimes preterm infants have obstructive apnea (an obstruction to the movement of air in their airways)
From page 322...
... is an acute injury of the small or large intestines that causes inflammation and injury to the bowel lining and that primarily affects preterm infants. NEC occurs in 3 percent of infants born before 33 weeks of gestation and in 7 percent of infants with birth weights less than 1,500 grams (Lee et al., 2000; Lemons et al., 2001; Smith et al., 2005)
From page 323...
... is common in preterm and full-term infants, often presents as regurgitation, and may adversely affect growth and health. It may also be manifested by aspiration pneumonia, wheezing,
From page 324...
... Covering the skin of preterm infants born before 26 weeks of gestation with a barrier ointment does not prevent but actually increases the risks of infection (Conner et al., 2003)
From page 325...
... The most serious manifestations of infections with these agents commonly seen in preterm infants include pneumonia, sepsis, meningitis, and urinary tract infections. As many as 65 percent of infants with birth weights of less than 1,000 grams have at least one infection during their initial hospitalization (Stoll et al., 2004)
From page 326...
... In preterm infants, the duct may not close properly, which results in a patent (open) ductus arteriosus, which can lead to heart failure and reduced blood flow to vital body organs (e.g., the kidney and the GI tract)
From page 327...
... . Hypotension is a frequent concern in preterm infants, but there is no consensus as to what the blood pressure readings should be in preterm infants with gestational ages of less than 26 or 27 weeks.
From page 328...
... Ventilated infants are at increased risk for otitis media. Significant hearing impairment, often requiring hearing aides, occurs in 1 to 5 percent of infants born at gestational ages of less than 25 or 26 weeks (Hintz et al., 2005; Vohr et al., 2005; Wood et al., 2000)
From page 329...
... It is a neovascular retinal disorder, and its incidence increases with decreasing gestational age and decreasing birth weight. It is multifactorial in etiology, with the primary determinant being immaturity with an avascular retina (Madan et al., 2005)
From page 330...
... ROP occurs in 16 to 84 percent of infants born with gestational ages of less than 28 weeks, 90 percent of infants with birth weights of less than 500 or 750 grams, and 42 to 47 percent of infants with birth weights of less than 1,000 or 1,500 grams (CRPCG, 1988, 1994; Fledelius and Greisen, 1993; Gibson et al., 1990; Gilbert et al., 1996; Lee et al., 2000; Lefebvre et al., 1996; Lucey et al., 2004; Mikkola et al., 2005; Repka, 2002)
From page 331...
... Screening ophthalmologic examinations require an experienced examiner and careful examination of the retina to the periphery with an indirect ophthalmoscope and lid speculum after dilation of the pupils. Revised guidelines for screening preterm infants for ROP have recently been published, with recommendations for which infants should be screened (infants with birth weights of less than 1,500 grams or gestational ages of less than 32 weeks or selected other preterm infants with an unstable clinical course)
From page 332...
... Infants born preterm also have more difficulties with the transition from placental support to extrauterine life and the many vascular changes that occur.
From page 333...
... The incidence and severity of IVH increase with decreasing gestational age and birth weight. Factors that contribute to IVH include hypotension, hypertension, fluctuating blood pressures, poor autoregulation of cerebral blood flow, disturbances in coagulation, hyperosmolarity, and injury to the vascular endothelium by oxygen free radicals.
From page 334...
... . The prevalence of neurodevelopmental disabilities in preterm infants with severe IVH and ventricular dilation or posthemorrhagic hydrocephalus ranges from 20 to 75 percent (de Vries et al., 2002; Fernell et al., 1994)
From page 335...
... carried by the blood can all contribute brain injury. A meta-analysis found significant relationships between clinical chorioamnionitis, PVL, and cerebral palsy in preterm infants (Wu and Colford, 2000)
From page 336...
... Complications for Near-Term or Late-Preterm Infants For many years, attention has focused on high-risk obstetric and neonatal intensive care for extremely preterm infants and infants born at the lower limit of viability, although very little attention has been paid to the majority of preterm infants who are born near term (also called late-preterm infants)
From page 337...
... the neuromaturation of infants born preterm. The NICU presents preterm infants with an overwhelming amount of stimuli because of the active hospital environment and the infant's exposure to multiple medical procedures (Aucott et al., 2002; Gilkerson et al., 1990)
From page 338...
... The ability to control the frequency, duration, and intensity of incoming stimuli is an important aspect of learning. Fetuses and preterm infants respond to sound and light as early as 24 to 26 weeks of gestation (Allen and Capute, 1986; Johansson et al., 1992)
From page 339...
... . The NICU bombards preterm infants with multiple, invariable stimuli, including bright fluorescent lights, noise, and frequent handling (Aucott et al., 2002; Chang et al., 2001; Robertson et al., 1998)
From page 340...
... may be painful. These frequent painful experiences that preterm infants encounter in an NICU could lead to structural and functional alterations of their nervous system and subsequent altered pain responses through childhood (Anand, 1998; Anand et al., 2001; Grunau et al., 1998, 2001)
From page 341...
... . Another series of studies demonstrated that more-preterm infants who were predominantly in the supine position in the NICU had asymmetries, asymmetric flattening of the skull, an early preference for use of the right hand, and an asymmetric gait (Konishi et al., 1986, 1987, 1997)
From page 342...
... 342 PRETERM BIRTH placed forward, and hips adducted to promote normal neuromaturation. Modeling of this approach for families in the NICU also enhances carryover to post-NICU care and promotes the parents' interest in providing neurodevelopmental support for their infant.
From page 343...
... Finding 10-1: Few postnatal intervention strategies that can be used to improve outcomes for children born preterm have been evalu ated, and such intervention strategies are needed, especially for more immature preterm infants. VARIATIONS IN NEONATAL COMPLICATION RATES The complications of the newborn period noted in this chapter reflect in part the difficulty of establishing extrauterine life with immature organs.
From page 344...
... CONCLUSIONS Although the mortality rate for preterm infants and the gestational agespecific mortality rate have dramatically improved over the last 3 to 4 decades, preterm infants remain vulnerable to the many complications of prematurity. Infants born at the lower limit of viability have the highest mortality rates and the highest rates of all complications of prematurity.
From page 345...
... The high rates of neurological injury in preterm infants highlight the need for better neuroprotective strategies and postnatal interventions that support the extrauterine neuromaturation and neurodevelopment of preterm infants. Long-term health and neurodevelopmental outcomes should be the focus of new trials of treatments and intervention strategies for neonates born preterm.


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