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.

• ~15% at 35weeks.

• ~8% at 36 weeks.

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.

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