Stacie Bennett, M.D. East Bay Newborn Specialists September 12, 2007 32-36 Week Infants Stacie Bennett, M.D. East Bay Newborn Specialists September 12, 2007

Definitions Full Term >37 weeks of gestation Preterm <34 weeks of gestation Late preterm 34 0/7-36 6/7 weeks of gestation Normal BW >2500grams LBW <2500g VLBW <1500g ELBW <1000g

Statistics Rate of preterm birth in US increased from 9.1% in 1981 to 12.3% in 2003. 2/3 of this increase was due to late preterm births. ~74% of preterm births are late preterm infants from 34-36 weeks of gestation. This leads to huge impact on health care.

Statistics ~50% of infants born at 34 weeks require intensive care.

Late Preterm Infant In 2005 the NICHD had a workshop to address the issues and impact of these late preterm infants. Prior to this meeting these infants were called “near term”. These infants have significantly higher rates of morbidities and mortalities compared to term infants and should be considered preterm.

Neonatal Issues of Late Preterm Infants Temperature Instability Hypoglycemia Respiratory distress Apnea Increased mortality and risk of SIDS Increased risk of sepsis/antibiotic exposure GI problems and feeding difficulties Hyperbilirubinemia Increased readmissions Long term neurodevelopmental problems

Temperature Instability Hypothermia: rectal temperature <36.5 degrees C. Late preterms are at increased risk for hypothermia through the first 24 hours of life. Probably secondary to immature epidermal barrier, increased surface area to weight ratio, more delivery room intervention preventing bundling, but also may be a sign of sepsis. 10% of infants at 35-36 weeks and ~0% at term require some type of management for hypothermia.

Temperature Instability Clinical signs of hypothermia include: tachypnea, poor color due to vasoconstriction, low heart rate, and metabolic acidosis. Management: Delivery room: routine NALS, warmers, skin to skin. ICN: may include skin to skin contact for larger stable infants, or extra bundling and hats, but often require a radiant warmer or isolette to maintain normal temperature (36.5-37.4 degrees C). Important to follow temperatures frequently for the first 24 hours.

Hypoglycemia Late preterms are at increased risk for hypoglycemia requiring treatment. ~18% at 35-36 weeks and 4% at term develop hypoglycemia. 2/3 of these infants require treatment with IV dextrose. The etiology is felt to be secondary to delay in hepatic glucose-6-phosphatase activity, low body fuel stores, inadequate oral intake, or other risk factors such as hypothermia and sepsis that increases metabolic demand.

Hypoglycemia The main concern: glucose is the primary substrate for cerebral metabolism. In preterm infants moderate hypoglycemia with glucose <47mg/dL has been shown to have neurodevelopmental consequences. Hypoglycemia can occur during the first 24 hours and needs to be monitored. Treatment may include: A nipple trial of formula or D10W if infant is able to. If unable to nipple, will require IV fluid with a D10W bolus of 2-3ml/kg followed by a dextrose infusion.

Respiratory Issues Increased risk for RDS, pulmonary hypertension, TTN, and Pneumonia(?). RDS can occur in ~12% of 33-34 wk, 2% of 35-36 wk, and 0.11% in term infants. TTN can occur in 11.6% of 33-34 wk, 5% of 35-36 wk, and <1% in term infants. Overall, ~31% of 35-36 weeks will have some respiratory distress requiring some management vs ~ 4% for term.

Respiratory Issues Etiology for distress is possibly due to lack of clearance of fluid with immature Na transport channels or surfactant deficiency. Must monitor for signs of distress: tachypnea, nasal flaring, retractions, grunting, oxygen need. Management may include: Monitoring Oxygen via a hood or nasal canula Use of nasal continuous positive airway pressure Intubation and surfactant therapy These infants are also at increased risk for apnea (4-5% at 34-36 weeks and ~0% at term) and must be monitored.

Infection Late preterm infants are more likely to be evaluated for sepsis and treated for presumed or actual infection. Therefore they have more antibiotic exposure. If an infant has respiratory distress, hypoglycemia, or hypothermia, it can be a sign of infection and may require a septic w/u including antibiotics. Perinatal history is also important, such as maternal chorio or prolonged rupture of membranes, as GBS status is often unknown at these gestations.

GI/Feeding Issues Late preterm infants have less mature peristaltic function and sphincter control. They are at increased risk for necrotizing enterocolitis (NEC). They can also have uncoordinated suck and swallow, poor weight gain, and dehydration. Management: IVF and parenteral nutrition until enteral feeding improves. Gavage feeds until oral feeding improves. Supplementation of breast milk with formula or higher calorie supplementation if inadequate weight gain.

Jaundice Late preterms have an increased incidence of hyperbilirubinemia. This often leads to delayed discharge and an increased rate of readmission. They appear to be at increased risk for bilirubin induced brain injury. A large proportion of infants with kernicterus are late preterm infants. Management: These infants need to be monitored closely for jaundice. Consider checking a bilirubin prior to discharge and plotting it on the graphs in the AAP guidelines if >35 weeks. These infants need close follow up after discharge.

Readmission Increased rate of readmission: 5.3-9.6% for infants from 33-37 weeks. 3.6-4.4% for term infants. Readmission may be secondary to jaundice, poor weight gain, dehydration, or other etiologies. They need close follow up as outpatients.

Mortality Increased mortality from all causes compared to infants born at term. 7.7/1000 in late preterm infants vs 2.5/1000 in term infants. 2 X greater risk for SIDS. 1.4/1000 in late preterm infants vs 0.7/1000 in term infants; mechanism is unknown.

Brain Late preterms have more immature brains. Weight is 60% of that at term. Decreased sulci/gyri/synapses. Some studies suggest increased risk of periventricular leukomalacia seen at autopsy. These infants are at increased risk for cerebral palsy as compared to term infants.

Long Term Outcome Limited data. Studies are primarily based on surveys. In follow-up studies, infants born at 32-35 weeks can have ~1/3 with some learning/behavioral difficulty. ~20% of 34-37 week infants can have some learning difficulties compared to <10% of those born at term. Other data suggest increased rates of ADHD and other behavioral problems.

What to do? Need more information. ? Best obstetric management, ? Later steroids, ? Check for fetal lung maturity. ? Elective c/sections. Best neonatal management- well baby vs ICN. Better studies evaluating long term follow up and how to improve outcomes.

32-33 week infant Same complications of the late preterm infant, though increased frequency. Require ICN admission. Infants between 30-34 weeks ~ 46% require assisted ventilation (CPAP or intubation) Most if not all require IV fluids and TPN. Prior to 34 weeks most infants can’t nipple all feeds and require gavage feedings. They are at risk for problems seen in more preterm infants. Even higher risk for developmental problems and readmissions.

Overall Infants <34 weeks and <2100 grams: admit to ICN, neonatology consult and perhaps transfer. 34-36 weeks: close observation for all of the above issues before transferring to well baby. Don’t discharge early. Close follow up after discharge and into childhood.

Bibliography Raju, Higgins, Stark, Leveno. Optimizing care and outcome for late-Preterm Infants: A summary of the workshop sponsored by the National Institute of Child Health and Human Development. Pediatrics 2006; 118:1207-1214. Wang, Dorer, Fleming, Catlin. Clinical Outcomes of Near-Term Infants. Pediatrics 2004; 114: 372-377. Kirkegaard, Obel, Hedegaard, Henriksen. Gestational Age and birth weight in relation to school performance of 10 year old children. Pediatrics 2006; 118: 1600-1607. Stein, Siegel, Bauman. Are children of moderately low birth weight at increased risk for poor health? Pediatrics 2006; 118: 217-224 Engle. A recommendation for the definition of “late Preterm” and the birth weight-Gestational age classification system. Seminars in Perinatology 2006; 30: 2-7 Laptook, Jackson. Cold Stress and Hypoglycemia in the late preterm infant. Seminars in Perinatology 2006; 30: 24-27 Escobar, et al. Unstudied infants: outcomes of moderately premature infants in the neonatal intensive care unit. Archives of diseases of childhood 2006; 91; F238-244. Shapiro-Mendoza et al. Risk factors for neonatal morbidity and mortality among “healthy’ late preterm newborns. Seminars in Perinatology. 2006; 30: 54-60. Huddy, Johnson, Hope. Educational and behavioral problems in babies of 32-35 weeks gestation. Archives of diseases of childhood fetal and neonatal edition. 2001; 85: F23-28. Jain, Eaton. Physiology of Fetal lung fluid clearance and the effect of labor. Seminars in perinatology 2006; 30: 34-43.