Primary-care clinicians assume care for patients of all ages. Treatment of newborn infants includes episodic wellness and preventative care as well as periodic illness care. Although guidelines for the primary care of neonates and infants are helpful in clinical practice protocols, the gestational age of the infant may be overlooked. Parental teaching related to care of the neonate and infant may be generalized to what would be expected for the term infant.
Neonatal intensive care units (NICUs) usually have protocols for parental training in the specialized home-care needs of the preterm neonate with some specification of expected differences in growth and developmental norms for the preterm infant compared with the term infant. Many require or recommend parental “rooming in” with the neonate for a period of time before discharge. However, “late preterm” infants may be overlooked in this specialized teaching since many of these neonates are not admitted to the NICU or, if they are, the stay is relatively short. This can be problematic and may contribute to increased morbidity in the late preterm infant.
What is a late preterm infant?
In 2005, an expert panel at a workshop convened by the National Institutes of Child Health and Human Development recommended that the newborn at 34 weeks 0 days (the age after which steroid injections are typically not administered to the mother) through 36 weeks 6 days gestation be referred to as late preterm. Preterm infants are known to have higher morbidity and mortality rates compared with term infants. The phrase late preterm conveys the concept that these infants are indeed preterm and not almost term.1 It has long been recognized that the infant born prematurely between 34 and 37 weeks' gestation is at higher risk for morbidity and mortality than those born before 28 weeks or after 37 weeks.2,3
Explaining increased risks
Reasons for the increased risk to the infant born within this 34- to 37-week time frame are not fully understood, but several have been suggested:
Misperceptions: The reference near term when used to describe the neonate born between 34 and 37 weeks, is perceived to equate to almost term, and therefore the child is treated as if she or he is term.4
Respiratory system dysfunction: The alveoli at 28 weeks' gestation are more sac-shaped with longer radii of curvature, thereby requiring less surfactant for stability than the 32- to 34-week alveoli, which are more circular. The normal surfactant surge begins at about 34-35 weeks' gestation; therefore these neonates have a relative surfactant deficiency and more chance of respiratory distress (perhaps of a subclinical nature).5 Feeding-related bradycardia, oxygen desaturation, and apnea of prematurity are common between 33 and 38 weeks' gestation.6
Glycemic instability: A term newborn's blood glucose stabilizes at about 40-60 mg/dL within the first two to four hours of life and should stabilize to 60-80 mg/dL by 12-24 hours. For the late preterm neonate, however, the increased energy demands for temperature regulation, increased respiratory effort, and other risks that may have been causative for the preterm delivery can cause the blood glucose to remain low for a prolonged period of time.7 In addition, poor coordination of suck-swallow sequence and suboptimal lactation may contribute to the poor glycemic control.8,9,10
Inadequate oral intake: Inadequate oral intake can contribute to the increased morbidity and mortality in the near-term infant.11 Although breastfeeding is beneficial in a number of ways for neonates of all gestational ages, the late-preterm infant is at increased risk of hyperbilirubinemia and kernicterus when breastfed due to decreased ability to suck and swallow.8,9 A systematic approach to monitoring bilirubin levels and targeted follow-up was shown to reduce adverse events.12
Susceptibility to infection: Immaturity of the immune system increases susceptibility to infection. The overlap of symptoms of infection and immaturity may lead to increased morbidity and mortality.13 The immaturity of the respiratory system decreases upper airway control, ventilatory responses to hypoxia and CO2 levels, and the stimulatory response of the respiratory system to excessive warmth or cooling.9
Neurologic immaturity: The immaturity of the neurologic system can lead to problems during the neonatal period, infancy, and throughout the preschool years. Approximately 50% of cortical development occurs between the 34th and 40th week of gestation. Between 36 and 40 weeks, the relative percentage of myelinated white matter and gray matter increases exponentially. There is increased incidence of developmental delay in the first three years of life, more need for referral to special-needs preschool resources, and more likelihood of insufficient school readiness in the child delivered in the late-preterm time frame.14