Health Risks Associated With Late-Preterm Infants
Studies conducted to determine indications for latepreterm delivery have found that spontaneous labor and premature rupture of membranes, pregnancy-related hypertension, placental accidents, fetal disorders, intrauterine growth restriction, multiple gestation, and maternal medical disorders were all associated with late-preterm births (Dimitriou et al., 2010; Lubow et al., 2009; McIntire & Leveno, 2008). However, two studies have shown that maternal medical conditions and late-preterm birth were independent risk factors for newborn morbidities (Dimitriou et al., 2010; Shapiro-Mendoza et al., 2008). Compared to term infants with no exposure, late-preterm infants born to mothers with antepartum hemorrhage were 12 times more likely to experience morbidity during the birth hospitalization, and those exposed to hypertensive disorders of pregnancy were 11 times more likely (Shapiro-Mendoza et al., 2008). Both Shapiro-Mendoza et al. (2008) and Dimitriou et al. (2010) showed that earlier gestational age had a greater effect on infant morbidity than maternal medical conditions; however, when early gestational age and maternal medical conditions were combined, the researchers saw an additive effect in newborn morbidity.
The mode of delivery has been analyzed for latepreterm infants and the effect on infant morbidity. Malloy (2009) analyzed United States birth and infant death certificates from 2000–2003, and found infants 32 to 36 weeks gestation had a higher risk of neonatal mortality and morbidity when born via primary cesarean section compared to vaginal delivery, independent of risk factors such as maternal demographic characteristics, medical complications, and labor and delivery complications. Another large prospective study (DeLuca, Boulvain, Irion, Berner, & Pfister, 2009) compared modes of delivery and found that both term and late-preterm infants born by elective cesarean section, when compared with a planned vaginal delivery, had significantly higher rates of mortality, admission to the neonatal intensive care unit, and respiratory morbidity, with gestational age an independent risk factor for morbidity. Lower gestational age resulted in higher incidence of morbidity (DeLuca et al., 2009). The results of this study suggest that elective cesarean section in the preterm infant has infant morbidity risks and should not be performed unless necessary (DeLuca et al., 2009).
Hyperbilirubinemia. Several studies have found an increased risk of hyperbilirubinemia in late-preterm infants (Sarici et al., 2004; Vachharajani & Dawson, 2009; Wang et al., 2004). Rehospitalization for jaundice occurs more frequently in late-preterm infants than in term infants (Escobar et al., 2005; Jain & Cheng, 2006; Tomashek et al., 2006). Late-preterm infants have an immature hepatic system with limited ability to conjugate bilirubin. When combined with the risk of inadequate fluid intake and dehydration, decreased excretion of bilirubin and increased enterohepatic circulation of bilirubin occurs (Dani et al., 2009; Mally et al., 2010). The risk of extremely high levels of bilirubin leading to kernicterus also exists (Mally et al., 2010). The American Academy of Pediatrics (AAP) and the Subcommittee on Hyperbilirubinemia (2004) released guidelines entitled, "Management of Hyperbilirubinemia in the Newborn Infant 35 or More Weeks of Gestation." These guidelines state that clinicians should "recognize that infants at less than 38 weeks' gestation, particularly those who are breastfed, are at higher risk of developing hyperbilirubinemia and require closer surveillance and monitoring" (AAP & the Subcommittee on Hyperbilirubinemia, 2004, p. 298).
Respiratory Compromise. A large multi-site retrospective study based on electronic records of newborns admitted to the NICU with respiratory compromise between 2002–2008 found 36.5% of the late-preterm infants were admitted to the NICU for evaluation of respiratory symptoms, compared to 7.2% of the term infants (Consortium on Safe Labor et al., 2010). Multiple studies have found that late-preterm infants are at increased risk for respiratory distress syndrome (RDS), transient tachypnea of the newborn (TTN), pneumonia, and air leaks (pneumothorax and pneumomediastinum) requiring respiratory support with the rate of respiratory complications steadily decreasing with each increasing week in gestational age (Consortium on Safe Labor et al., 2010; Kamath, Marcotte, & DeFranco, 2011; Vachharajani & Dawson, 2009; Wang et al., 2004).
Hypoglycemia and Poor Feeding. In a study conducted by Wang et al. (2004), 76% of the near-term infants (defined as 35 to 36 and 6/7 weeks gestation) with poor feeding had a prolonged hospitalization, compared to the 28.6% of term infants who had poor feeding. Hypoglycemia was found three times as often in the near-term infants compared with the term infants, and nearly twothirds of the near-term infants required treatment with intravenous dextrose (Wang et al., 2004). Dani et al. (2009) suggested that hypoglycemia in the late-preterm infant may be due to deficient glycogenolysis and gluconeogenesis; however, poor feeding remains a plausible cause for hypoglycemia as well.
Issues such as hypoglycemia, jaundice, and temperature instability, which are common problems for latepreterm infants, can contribute to a decreased state of arousal with early fatigue during feeding that leads to less intake (Ludwig, 2007). Muscle tone, physiologic stability, oral motor control, and alert state may not be fully developed in the late-preterm infant (Ludwig, 2007; Palmer, 1993). Jain and Cheng (2006) found that 7.5% of latepreterm infants were readmitted to the hospital for feeding problems, compared to 5% of the term infants. The rate of readmission for late-preterm breastfed infants was more than double the rate for breastfed term infants (Tomashek et al., 2006).
Temperature Instability. Wang et al. (2004) found near-term infants were 10% more likely than full-term newborns to have temperature instability. Pulver et al. (2010) found that 31% of the infants studied had hypothermia requiring an isolette, causing 82% of these infants to have a prolonged hospital stay. Jain and Cheng (2006) found that late-preterm infants also had a higher risk of being readmitted to the hospital for hypothermia than term infants (2.5% vs. 0.2%). Late-preterm infants have an immature epidermal barrier and a higher ratio of surface area to birth weight than term infants, making this population more likely to have cold stress (Mally et al., 2010). Late-preterm infants also have less white adipose tissue for insulation and less accumulation of brown adipose tissue, making the infants less able to generate heat from brown adipose tissue as term infants do for thermal regulation (Engle et al., 2007).
Infection. Because late-preterm infants often exhibit signs of a possible infection, such as respiratory distress, temperature instability, and hypoglycemia, late-preterm infants are frequently evaluated for a suspected infection. Wang et al. (2004) found that the near-term population studied was three times more likely to be evaluated for sepsis than term infants. Pulver et al. (2010) found that 11% of the late-preterm infants studied had a prolonged hospital stay for treatment of suspected sepsis. Jain and Cheng (2006) found that 8.2% of late-preterm infants were readmitted to the hospital for suspected infection, compared to 6.6% of term infants admitted for infection.
Early Discharge From the Hospital. Because the latepreterm infant is often the same height and weight as a fullterm infant and in the initial newborn period is able to maintain his or her temperature and breast or bottle feed, the late-preterm infant may be discharged early from the hospital. Early discharge is defined as less than 48 hours after a vaginal birth or 96 hours after a cesarean section (AAP & the Committee on Fetus and Newborn, 2010). The late-preterm infant's instability in adapting to extra uterine life may not be discovered during the birth hospitalization if the infant is discharged early (Escobar et al., 2005). The AAP recommends that early discharge should be limited to singleton births with gestational ages 38 to 42 weeks; however, discharge of the late-preterm population still occurs (AAP & the Committee on Fetus and Newborn, 2010; Goyal, Fager, & Lorch, 2011).
Early discharge is not recommended due to the multiple morbidity risks associated with late-preterm infants. In a retrospective chart review of 235 late-preterm infants, 40% of the infants experienced a prolonged hospital stay; 75% of the 34-week gestation infants and 25% of the 36-week gestation infants experienced prolonged hospital stays due to oxygen need, phototherapy for hyperbilirubinemia, hypothermia, need for nasogastric feedings, or antibiotic administration greater than three days (Pulver et al., 2010). In a large multi-site study, Shapiro-Mendoza et al. (2008) found that 22.2% of the 26,170 late-preterm births had experienced at least one complication that could lead to a prolonged hospital stay, compared to 3% of the 377,638 term infants; the 34-week gestation age group had the highest morbidity (51%), and the percentage gradually decreased with each advancing week, down to 5.9% morbidity at 37 weeks gestation.
Literature Review
Birth History and Late-preterm Incidence
Studies conducted to determine indications for latepreterm delivery have found that spontaneous labor and premature rupture of membranes, pregnancy-related hypertension, placental accidents, fetal disorders, intrauterine growth restriction, multiple gestation, and maternal medical disorders were all associated with late-preterm births (Dimitriou et al., 2010; Lubow et al., 2009; McIntire & Leveno, 2008). However, two studies have shown that maternal medical conditions and late-preterm birth were independent risk factors for newborn morbidities (Dimitriou et al., 2010; Shapiro-Mendoza et al., 2008). Compared to term infants with no exposure, late-preterm infants born to mothers with antepartum hemorrhage were 12 times more likely to experience morbidity during the birth hospitalization, and those exposed to hypertensive disorders of pregnancy were 11 times more likely (Shapiro-Mendoza et al., 2008). Both Shapiro-Mendoza et al. (2008) and Dimitriou et al. (2010) showed that earlier gestational age had a greater effect on infant morbidity than maternal medical conditions; however, when early gestational age and maternal medical conditions were combined, the researchers saw an additive effect in newborn morbidity.
The mode of delivery has been analyzed for latepreterm infants and the effect on infant morbidity. Malloy (2009) analyzed United States birth and infant death certificates from 2000–2003, and found infants 32 to 36 weeks gestation had a higher risk of neonatal mortality and morbidity when born via primary cesarean section compared to vaginal delivery, independent of risk factors such as maternal demographic characteristics, medical complications, and labor and delivery complications. Another large prospective study (DeLuca, Boulvain, Irion, Berner, & Pfister, 2009) compared modes of delivery and found that both term and late-preterm infants born by elective cesarean section, when compared with a planned vaginal delivery, had significantly higher rates of mortality, admission to the neonatal intensive care unit, and respiratory morbidity, with gestational age an independent risk factor for morbidity. Lower gestational age resulted in higher incidence of morbidity (DeLuca et al., 2009). The results of this study suggest that elective cesarean section in the preterm infant has infant morbidity risks and should not be performed unless necessary (DeLuca et al., 2009).
Morbidities in the Late-preterm Infant
Hyperbilirubinemia. Several studies have found an increased risk of hyperbilirubinemia in late-preterm infants (Sarici et al., 2004; Vachharajani & Dawson, 2009; Wang et al., 2004). Rehospitalization for jaundice occurs more frequently in late-preterm infants than in term infants (Escobar et al., 2005; Jain & Cheng, 2006; Tomashek et al., 2006). Late-preterm infants have an immature hepatic system with limited ability to conjugate bilirubin. When combined with the risk of inadequate fluid intake and dehydration, decreased excretion of bilirubin and increased enterohepatic circulation of bilirubin occurs (Dani et al., 2009; Mally et al., 2010). The risk of extremely high levels of bilirubin leading to kernicterus also exists (Mally et al., 2010). The American Academy of Pediatrics (AAP) and the Subcommittee on Hyperbilirubinemia (2004) released guidelines entitled, "Management of Hyperbilirubinemia in the Newborn Infant 35 or More Weeks of Gestation." These guidelines state that clinicians should "recognize that infants at less than 38 weeks' gestation, particularly those who are breastfed, are at higher risk of developing hyperbilirubinemia and require closer surveillance and monitoring" (AAP & the Subcommittee on Hyperbilirubinemia, 2004, p. 298).
Respiratory Compromise. A large multi-site retrospective study based on electronic records of newborns admitted to the NICU with respiratory compromise between 2002–2008 found 36.5% of the late-preterm infants were admitted to the NICU for evaluation of respiratory symptoms, compared to 7.2% of the term infants (Consortium on Safe Labor et al., 2010). Multiple studies have found that late-preterm infants are at increased risk for respiratory distress syndrome (RDS), transient tachypnea of the newborn (TTN), pneumonia, and air leaks (pneumothorax and pneumomediastinum) requiring respiratory support with the rate of respiratory complications steadily decreasing with each increasing week in gestational age (Consortium on Safe Labor et al., 2010; Kamath, Marcotte, & DeFranco, 2011; Vachharajani & Dawson, 2009; Wang et al., 2004).
Hypoglycemia and Poor Feeding. In a study conducted by Wang et al. (2004), 76% of the near-term infants (defined as 35 to 36 and 6/7 weeks gestation) with poor feeding had a prolonged hospitalization, compared to the 28.6% of term infants who had poor feeding. Hypoglycemia was found three times as often in the near-term infants compared with the term infants, and nearly twothirds of the near-term infants required treatment with intravenous dextrose (Wang et al., 2004). Dani et al. (2009) suggested that hypoglycemia in the late-preterm infant may be due to deficient glycogenolysis and gluconeogenesis; however, poor feeding remains a plausible cause for hypoglycemia as well.
Issues such as hypoglycemia, jaundice, and temperature instability, which are common problems for latepreterm infants, can contribute to a decreased state of arousal with early fatigue during feeding that leads to less intake (Ludwig, 2007). Muscle tone, physiologic stability, oral motor control, and alert state may not be fully developed in the late-preterm infant (Ludwig, 2007; Palmer, 1993). Jain and Cheng (2006) found that 7.5% of latepreterm infants were readmitted to the hospital for feeding problems, compared to 5% of the term infants. The rate of readmission for late-preterm breastfed infants was more than double the rate for breastfed term infants (Tomashek et al., 2006).
Temperature Instability. Wang et al. (2004) found near-term infants were 10% more likely than full-term newborns to have temperature instability. Pulver et al. (2010) found that 31% of the infants studied had hypothermia requiring an isolette, causing 82% of these infants to have a prolonged hospital stay. Jain and Cheng (2006) found that late-preterm infants also had a higher risk of being readmitted to the hospital for hypothermia than term infants (2.5% vs. 0.2%). Late-preterm infants have an immature epidermal barrier and a higher ratio of surface area to birth weight than term infants, making this population more likely to have cold stress (Mally et al., 2010). Late-preterm infants also have less white adipose tissue for insulation and less accumulation of brown adipose tissue, making the infants less able to generate heat from brown adipose tissue as term infants do for thermal regulation (Engle et al., 2007).
Infection. Because late-preterm infants often exhibit signs of a possible infection, such as respiratory distress, temperature instability, and hypoglycemia, late-preterm infants are frequently evaluated for a suspected infection. Wang et al. (2004) found that the near-term population studied was three times more likely to be evaluated for sepsis than term infants. Pulver et al. (2010) found that 11% of the late-preterm infants studied had a prolonged hospital stay for treatment of suspected sepsis. Jain and Cheng (2006) found that 8.2% of late-preterm infants were readmitted to the hospital for suspected infection, compared to 6.6% of term infants admitted for infection.
Early Discharge From the Hospital. Because the latepreterm infant is often the same height and weight as a fullterm infant and in the initial newborn period is able to maintain his or her temperature and breast or bottle feed, the late-preterm infant may be discharged early from the hospital. Early discharge is defined as less than 48 hours after a vaginal birth or 96 hours after a cesarean section (AAP & the Committee on Fetus and Newborn, 2010). The late-preterm infant's instability in adapting to extra uterine life may not be discovered during the birth hospitalization if the infant is discharged early (Escobar et al., 2005). The AAP recommends that early discharge should be limited to singleton births with gestational ages 38 to 42 weeks; however, discharge of the late-preterm population still occurs (AAP & the Committee on Fetus and Newborn, 2010; Goyal, Fager, & Lorch, 2011).
Early discharge is not recommended due to the multiple morbidity risks associated with late-preterm infants. In a retrospective chart review of 235 late-preterm infants, 40% of the infants experienced a prolonged hospital stay; 75% of the 34-week gestation infants and 25% of the 36-week gestation infants experienced prolonged hospital stays due to oxygen need, phototherapy for hyperbilirubinemia, hypothermia, need for nasogastric feedings, or antibiotic administration greater than three days (Pulver et al., 2010). In a large multi-site study, Shapiro-Mendoza et al. (2008) found that 22.2% of the 26,170 late-preterm births had experienced at least one complication that could lead to a prolonged hospital stay, compared to 3% of the 377,638 term infants; the 34-week gestation age group had the highest morbidity (51%), and the percentage gradually decreased with each advancing week, down to 5.9% morbidity at 37 weeks gestation.