📌 Section 119.3 – Moderate and Late Preterm Infants (Nelson's 22e) Core Summary

1. Definitions & Epidemiology
• Moderate preterm: 32 0/7 to 33 6/7 weeks gestation.
• Late preterm: 34 0/7 to 36 6/7 weeks gestation (formerly called "near-term").
• Late preterm account for ~75% of all preterm births; moderate ~11.5%.
• Mortality: late preterm 4-fold higher than term (8.2 vs 2.1 per 1000 live births); moderate preterm ~10-fold higher.
• Incidence has increased since 2015, with racial/ethnic disparities (higher in non-Hispanic Black and Hispanic populations).

2. Etiology
• Spontaneous preterm labor (most common), PPROM, multiple gestation, maternal hypertension/preeclampsia, placental abruption, fetal distress, iatrogenic delivery.
• Antenatal corticosteroids at 34-36 weeks are recommended by ACOG if preterm labor is threatened and no prior steroids given.

3. Moderate Preterm (32-33 wk) Morbidities
• Temperature instability, respiratory distress (RDS, TTN), apnea of prematurity, sepsis, hypoglycemia, hyperbilirubinemia, feeding difficulties, longer hospital stay (mean ~33 days).
• ROP screening not routinely recommended unless birthweight <1500 g or significant cardiopulmonary compromise.

4. Late Preterm (34-36 wk) Morbidities
• Overall morbidity risk ~7× higher than term infants; mortality risk ~4× higher.
• Hypoglycemia: Immature glycogen stores, high risk in first 24h. Screen at 1-2h of life, treat with early feeding or IV dextrose.
• Respiratory distress: RDS (surfactant deficiency, up to 30% risk at 34 wk), TTN (delayed lung fluid clearance). May require nCPAP or surfactant.
• Apnea: Less common than extremely preterm but can occur, especially if sepsis or hypoglycemia.
• Hyperbilirubinemia: Higher risk of severe indirect hyperbilirubinemia and kernicterus. Use hour-specific nomogram, lower phototherapy thresholds.
• Feeding difficulties: Immature suck-swallow-breathe coordination, poor oral intake → dehydration, weight loss, hypernatremia.
• Temperature instability: Hypothermia common due to higher surface area-to-mass ratio and decreased subcutaneous fat.
• Rehospitalization: Rate 2-3× higher than term infants (jaundice, feeding problems, respiratory infections, RSV).

5. Management & Discharge
• Delivery at hospital with appropriate neonatal care (Level II or III).
• Universal newborn care plus monitoring for hypoglycemia (glucose at 1-2h), hyperbilirubinemia (TSB or TcB at 24h or earlier if jaundiced), temperature regulation, respiratory status.
• Early follow-up within 48h of discharge for weight, feeding, jaundice, and hydration.
• Late preterm infants should NOT be managed as term infants; they require closer observation, sometimes in a NICU or special care nursery.
• Palivizumab for RSV prophylaxis may be indicated based on gestational age and comorbidities.

6. Long-term Outcomes
• Increased risk of lower school readiness, academic difficulties, ADHD, and behavioral problems compared to term peers.
• Higher risk of SIDS (sudden infant death syndrome).
• Continued surveillance for developmental delays and early intervention referral as needed.

💡 Pearls: Never dismiss a late preterm infant as "near-term" — they have significant physiologic immaturity. Hypoglycemia and hyperbilirubinemia are the most common preventable causes of readmission. Early follow-up (within 48h) is critical.