What is the pathophysiology of newborn care?

Pathophysiology of Newborn Transition

The transition from intrauterine to extrauterine life involves rapid cardiopulmonary adaptation, with approximately 85% of term newborns initiating spontaneous respirations within 10-30 seconds of birth, while 10% require drying and stimulation, and only 3-5% need positive pressure ventilation or more advanced resuscitation. 1

Normal Physiologic Transition

The fetal-to-neonatal transition requires immediate anatomic and physiologic adjustments to convert from placental gas exchange to pulmonary respiration 1:

• Initiation of air breathing triggers marked relaxation of pulmonary vascular resistance, dramatically increasing pulmonary blood flow and returning well-oxygenated blood to the left atrium and ventricle 1

• Removal of the placental circuit increases systemic vascular resistance and blood pressure, reducing right-to-left shunting across the ductus arteriosus 1

• Systemic organs must rapidly adjust to the dramatic increase in blood pressure and oxygen exposure 1

• Thermoregulation shifts from intrauterine thermostability to neonatal thermoregulation, inherently increasing oxygen consumption 1

Critical Timing of Transition Events

The majority of healthy term newborns follow a predictable pattern 1:

• 85% initiate spontaneous respirations within 10-30 seconds of birth 1
• Additional 10% respond during drying and stimulation 1
• 3% require positive-pressure ventilation to initiate respirations 1
• 2% require intubation for respiratory support 1
• 0.1% require chest compressions and/or epinephrine for successful transition 1

Pathophysiology of Impaired Transition in Preterm Infants

Preterm infants face unique vulnerabilities due to developmental immaturity 1, 2:

Cardiovascular Instability

• Hypotension occurs in 24-40% of infants weighing less than 1000g at birth, particularly in the first day of life 1

• Impaired cerebral autoregulation creates a narrower and lower pressure range with decreasing gestational age, making preterm brains vulnerable to both hypoperfusion and hyperperfusion injury 1

• Endotracheal intubation with positive pressure ventilation increases central venous pressure, which combined with hypotension episodes, leads to poor cerebral perfusion 1

Pulmonary Pathophysiology

• Surfactant deficiency in preterm infants leads to atelectasis and over-distension, with hyaline membranes blocking small airways 2

• Ventilation-perfusion mismatch occurs due to airway inhomogeneity, contributing to inflammation that progresses to bronchopulmonary dysplasia 2

• Incomplete arterial ingrowth into deep white matter and fragile germinal matrix vasculature increase vulnerability to intraventricular hemorrhage (IVH) 1

Hemorrhagic Complications

• Approximately 10% of preterm infants with any IVH and 20% with severe IVH will require permanent shunt placement for posthemorrhagic hydrocephalus 1

• Germinal matrix hemorrhage results from a hypoperfusion-reperfusion pattern affecting the immature vasculature that lacks adequate muscularis layer development for autoregulation 1

Immediate Postnatal Care Considerations

Skin-to-Skin Contact

• Immediate skin-to-skin care stabilizes newborn body temperature, prevents hypothermia, stabilizes blood glucose, decreases crying, and provides cardiorespiratory stability, especially in late preterm newborns 1

• Sudden unexpected postnatal collapse (SUPC) is a rare but potentially fatal event with an incidence of 2.6 to 133 cases per 100,000 newborns, with 73% occurring in the first 2 hours of life 1

• Continuous staff observation with frequent vital sign recording is prudent during the first few hours, particularly during skin-to-skin care and unsupervised breastfeeding attempts 1

Metabolic Considerations

• Intrapartum maternal glucose infusion can produce maternal hyperglycemia with subsequent fetal hyperglycemia, fetal metabolic acidosis, and rebound neonatal hypoglycemia 3

• Neonates, especially premature infants with low birth weight, require close monitoring during intravenous glucose treatment to ensure adequate glycemic control and avoid long-term adverse effects 3

• Hyponatremia risk is increased in children including neonates, who are at particular risk for developing hyponatremic encephalopathy 3

Risk-Appropriate Care Delivery

Infants born at <32 weeks' gestation, weighing <1500g, or with serious medical/surgical conditions should be delivered at Level III facilities to optimize outcomes and reduce mortality 1:

• Level III facilities provide continuous life support with advanced respiratory support, subspecialty consultants, and advanced imaging capabilities 1

• Level IV facilities add capabilities for surgical repair of complex conditions including congenital cardiac malformations requiring cardiopulmonary bypass 1

• Regionalized perinatal care systems ensure each newborn is delivered and cared for in the most appropriate facility for their health care needs 1

Common Pitfalls to Avoid

• Elective cesarean birth or labor induction may interfere with hormonal preparation for birth, including reversal of lung fluid secretion to absorption and pulmonary surfactant secretion 4

• Immediate umbilical cord clamping may compromise normal newborn transition by preventing adequate placental transfusion 4

• Excessive or rapid fluid administration in very low birth weight infants may increase serum osmolality and risk of intracerebral hemorrhage 3