Prematurity and Perinatal Pharm

Question 1

Prematurity

Definitions

Answer 1

• Prematurity: babies born alive before 37 wks of pregnancy are completed
  
  • Sub-categories:
    
    • Extremely preterm ⇒ < 28 wks gestational age [GA]
    • Very preterm ⇒ 28 to 32 wks GA
    • Preterm ⇒ 32 to 34 wks, GA
    • Late preterm ⇒ 35-37 wks GA
• Limit of viability: earliest GA at which the infant has < 50% chance of survival
  
  • 23 wks or 500g

Question 2

Preterm Birth

Etiologies

Answer 2

• Spontaneous
• Early induction of labor or caesarean birth
• Common causes:
  
  • Multiple pregnancies
  • Infections
  • Chronic conditions such as DM and HTN
  • Genetic influence
• Often no cause is identified

Question 3

Preterm Birth

Epidemiology

Answer 3

• Preterm birth affected ~ 1/10 infants born in the US
• Leading cause of mortality and morbidity in the newborn period
• Racial and ethnic differences in preterm birth rates remain
• Rates higher in African American individuals

Question 4

Preterm Birth

Consequences

Answer 4

Babies who survive preterm birth are at risk for:

• Respiratory:
  
  • Respiratory distress syndrome (RDS, formerly hyaline membrane disease [HMD])
  • Chronic lung disease (previously called bronchopulmonary dysplasia or BPD)
• Neurological problems:
  
  • Apnea of prematurity
  • Intraventricular hemorrhage (IVH)
  • Cerebral palsy
  • Developmental delays
• Cardiovascular:
  
  • Patent ductus arteriosus (PDA)
• Gastrointestinal and metabolic:
  
  • Hypoglycemia
  • Feeding difficulties
  • Osteopenia of prematurity
  • Necrotizing enterocolitis (NEC)
• Hematologic:
  
  • Anemia of prematurity
  • Thrombocytopenia
  • Hyperbilirubinemia
• Infection including sepsis, meningitis, pneumonia
• Vision problems:
  
  • Retinopathy of prematurity
• Auditory:
  
  • Hearing loss

Question 5

Respiratory Distress Syndrome

Pathophysiology

Answer 5

Due to surfactant deficiency

• Impaired surfactant synthesis and secretion ⇒ atelectasis, V/Q mismatch, and hypoventilation ⇒ hypoxemia and hypercarbia
• Respiratory and metabolic acidosis ⇒ pulmonary vasoconstriction ⇒ impaired endothelial and epithelial integrity ⇒ leakage of proteinaceous exudate ⇒ formation of hyaline membranes
• Relative deficiency of surfactant ⇒ ↓ lung compliance and functional residual capacity & ↑ dead space
• Resulting large V/Q mismatch and right-to-left shunt may involve as much as 80% of cardiac output
• Incidence and severity of RDS inversely related to gestational age
  
  • Most premature infants at the highest risk
  • Risk higher in babies of mothers who received no perinatal steroids

Question 6

Surfactant