Elsevier

Clinics in Perinatology

Volume 38, Issue 3, September 2011, Pages 493-516
Clinics in Perinatology

Outcomes of Preterm Infant
Morbidity and Mortality in Late Preterm and Early Term Newborns: A Continuum

https://doi.org/10.1016/j.clp.2011.06.009Get rights and content

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Definitions

Late preterm and early term newborns include infants that are categorized as infants born at 34 0/7 to 36 6/7 weeks’ gestation and 37 0/7 to 38 6/7 weeks’ gestation, respectively (Fig. 1). Late preterm was defined by participants at a 2005 workshop of the Eunice Kennedy Shriver National Institutes of Child Health and Human Development of the National Institutes of Health to address an emerging body of evidence that such infants had higher rates of morbidity and mortality than was generally

Magnitude of late preterm and early term births

The percentage of live births in the United States that were born late preterm increased between 1990 and 2006 from 7.3% to 9.14%, a 25% increase.11 This increase accounted for 84% of the increase in the rate of prematurity during that same 16-year period. During 2007 and 2008, the percentage of live births that were late preterm decreased by 3% to 8.77% of all live births (about 15,000 fewer late preterm births). Although this trend is encouraging, the percentage of live births born late

Acute Medical Morbidities and Mortality

Late preterm and early term infants are physiologically and metabolically less mature than late term infants. Risks of respiratory distress and death and/or a severe neurologic disorder are inversely associated with gestational age (Figs. 2 and 3).3, 6, 8, 9, 23, 24 In a population-based study of 150,426 live-born infants, severe respiratory failure (ie, treatment with mechanical ventilation and/or nasal continuous positive airway pressure) decreased from 20% at 34 weeks’ gestation to 0.3% at

Management of late preterm and early term infants

The focus of care of late preterm and early term infants is individualized depending on the specific medical and social issues that may occur. Counseling of women by pediatric and obstetric caregivers about the possible outcomes for late preterm and term infants is important when delivery of such infants is indicated so that families are informed of possible morbidities, admission to neonatal intensive care, prolonged birth hospitalizations, and readmission for hospital care. If delivery of

Causes of late preterm and early term births

Preterm births have increased for many reasons including demographic changes of women who become pregnant (such as delayed childbearing), infertility treatments, increased maternal age, increased multiple gestations, and maternal comorbid conditions including obesity.58 Several risk factors have been identified for late preterm and, by extrapolation, early term births.58, 59, 60 Late preterm birth has been associated with chorioamnionitis (relative risk, 3.1; 95% confidence interval, 2.6–3.7),

Summary

Late preterm and early term infants have significantly greater risks of medical complications and morbidities during the birth hospitalization and during the first weeks after birth than term infants. Neonatal and infant mortality and morbidity rates are largely influenced by gestational age with the lowest rates at 39 to 40 weeks’ gestation. Neonatal morbidity and mortality are significantly increased by maternal or fetal illness. Long-term morbidities occur in a small, but significant,

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