Neonatal Transition

Learning objectives

After completing this chapter, you should be able to:

1. Explain the respiratory, circulatory, thermal, and metabolic changes required during transition from fetal to neonatal life.
2. Describe how lung aeration lowers pulmonary vascular resistance and redirects cardiac output through the lungs.
3. Explain how cord clamping raises systemic vascular resistance and promotes functional closure of the fetal shunts.
4. Recognize a newborn who is transitioning normally versus one who requires warming, stimulation, oxygen, continuous positive airway pressure, or positive-pressure ventilation.
5. Use heart rate, respiratory effort, tone, preductal oxygen saturation, temperature, glucose, and perfusion to trend neonatal response.
6. Explain why preterm newborns have less respiratory, thermal, metabolic, and neurologic reserve.
7. Describe the correct purpose and limitations of the Apgar score.
8. Anticipate transport problems in newborns exposed to maternal magnesium, opioids, anesthesia, hypothermia, infection, or difficult delivery.
9. Prepare a neonatal transport environment that maintains ventilation, oxygenation, temperature, glucose, monitoring, and securement.

Opening transport scenario

A 34-week newborn is delivered shortly before the transport team reaches a rural emergency department. The newborn is limp, has irregular gasping respirations, and a heart rate of 88/min. The room is cool, the infant is wet, and no blended oxygen source is connected. This is not primarily a “cardiac” problem. The most likely immediate failure is inadequate lung inflation and gas exchange during the transition from placental to pulmonary support.

1. Birth is a multisystem transition

Before birth, the placenta performs gas exchange, the lungs are fluid filled, pulmonary vascular resistance is high, and the fetal shunts direct blood away from the pulmonary circulation. At birth, the newborn must establish ventilation, replace lung fluid with air, increase pulmonary blood flow, redirect cardiac output, maintain body temperature, and begin independent glucose regulation—often within minutes.[1,2]

2. Establishing ventilation and functional residual capacity

The fetal lungs contain liquid. During labor and after birth, fluid is cleared through epithelial sodium transport, thoracic recoil, lymphatics, and pulmonary blood vessels. The first effective breaths require enough pressure to move fluid, open alveoli, and establish a stable volume of air remaining after exhalation—functional residual capacity (FRC).

3. Circulatory transition and fetal-shunt closure

Two events drive the cardiovascular transition: lung aeration lowers pulmonary vascular resistance, and umbilical cord clamping removes the low-resistance placental circulation and raises systemic vascular resistance. These changes alter pressure relationships across the fetal shunts.

4. Rapid initial assessment

Current neonatal resuscitation guidance emphasizes preparation before birth, immediate assessment, thermal protection, and timely ventilation. The newborn’s heart rate is the most useful objective measure of response. Auscultation is used initially; electrocardiography provides rapid and accurate continuous heart-rate assessment during active resuscitation, while pulse oximetry is required to guide oxygen therapy.[1]

5. Initial steps and positive-pressure ventilation

For a newborn who is not transitioning normally, initial actions are to warm and maintain normal temperature, dry when appropriate, position the airway, stimulate, and clear the airway only when needed. A newborn who remains apneic or gasping, or whose heart rate remains below 100/min after initial steps, should receive assisted ventilation within the first 60 seconds after birth.[1]

Ventilation may begin with 21% oxygen in term and late-preterm newborns. Current guidance recommends 21%–30% oxygen for infants approximately 32–35 weeks and individualized higher starting concentrations for very preterm infants, with adjustment using preductal pulse oximetry and target saturations.[1] Follow your local NRP implementation and equipment capabilities.

6. Advanced escalation

If the heart rate does not rise, correct ventilation before advancing. Consider mask repositioning, airway repositioning, suction when obstruction is suspected, opening the mouth, increasing pressure judiciously, and placement of an alternative airway. Chest compressions are indicated when the heart rate remains below 60/min despite at least 30 seconds of ventilation that moves the chest, preferably through an endotracheal tube or laryngeal mask. Compressions are coordinated at a 3:1 ratio with ventilation. Vascular access and epinephrine are considered when the heart rate remains below 60/min despite effective ventilation and compressions.[1]

7. Thermoregulation

Newborns lose heat rapidly because of a large surface-area-to-mass ratio, wet skin, limited insulation, and limited ability to generate heat. Cold stress increases oxygen and glucose consumption and can worsen pulmonary vasoconstriction, hypoglycemia, and metabolic acidosis. The goal is normothermia—not overheating. WHO defines hypothermia as a temperature below 36.5°C; sick and preterm newborns require continuous thermal support and temperature monitoring.[3]

8. Metabolic transition and glucose

After the cord is clamped, continuous maternal glucose delivery stops. The newborn must mobilize glycogen, use fat stores, and establish feeding. Prematurity, hypothermia, sepsis, maternal diabetes, growth restriction, respiratory distress, and prolonged resuscitation increase the risk of hypoglycemia. Postresuscitation monitoring should include blood glucose when indicated, but treatment thresholds and infusion strategies must follow neonatal protocols and medical direction.

9. Why preterm newborns have less reserve

10. The Apgar score: useful, but not a resuscitation trigger

The Apgar score describes the newborn’s condition and response to intervention at defined time points. It is assigned at 1 and 5 minutes; if the 5-minute score is below 7, scoring is typically repeated every 5 minutes through 20 minutes. The score must not delay resuscitation and should not be used alone to predict an individual infant’s neurologic outcome.[4]

11. Medication-exposed newborn

Maternal medications may alter neonatal transition. The transport clinician should obtain the medication, dose, route, timing, and maternal renal function whenever relevant.

12. Postresuscitation care and transport

Newborns who require more than routine initial steps are at risk for recurrent apnea, hypoxemia, hypoglycemia, hypothermia, abnormal tone, seizures, and hemodynamic instability. Reassessment must continue during every movement and equipment change.[1]

13. Evolving case study

Phase 1: Failure to establish effective breathing

The 34-week newborn remains apneic with a heart rate of 88/min after warming, positioning, drying, and stimulation. The team begins positive-pressure ventilation with an appropriately sized mask and blended oxygen. There is minimal chest movement and the heart rate remains 86/min.

Interpretation: Ventilation is not yet effective. Reposition the airway, improve the mask seal, open the mouth, assess for obstruction, adjust pressure to achieve lung inflation, and consider an alternative airway if the heart rate does not rise.

Phase 2: Response to ventilation

After corrective steps, the chest moves gently and the heart rate rises to 132/min. Spontaneous respirations begin, but the infant has grunting and retractions. Preductal SpO₂ is rising through the expected transitional range.

Interpretation: The rise in heart rate confirms effective ventilation. A spontaneously breathing preterm newborn with ongoing work of breathing may benefit from continuous positive airway pressure according to protocol and available expertise.

Phase 3: New transport risk

Twenty minutes later, the infant’s axillary temperature is 35.9°C and glucose is trending down. The transport isolette has not been preheated.

Decision: Correct the thermal environment before departure, initiate glucose management according to neonatal orders, and reassess respiratory support. Hypothermia increases oxygen and glucose consumption and can destabilize an infant who initially appeared improved.

14. High-yield chapter summary

1. Birth requires rapid conversion from placental gas exchange to pulmonary gas exchange.
2. Lung aeration and oxygenation lower pulmonary vascular resistance and increase pulmonary blood flow.
3. Cord clamping raises systemic vascular resistance and removes the placental circulation.
4. Pressure changes promote functional closure of the foramen ovale; oxygenation promotes ductus arteriosus constriction.
5. Heart rate is the primary objective indicator of effective neonatal ventilation.
6. Apnea, gasping, or persistent heart rate below 100/min after initial steps requires positive-pressure ventilation.
7. Ventilation should be corrected before chest compressions are started.
8. Preductal pulse oximetry guides oxygen therapy; normal saturation rises gradually after birth.
9. Hypothermia increases oxygen and glucose demand and can worsen acidosis and pulmonary vasoconstriction.
10. Preterm newborns have less surfactant, weaker respiratory mechanics, limited thermal and glucose stores, and fragile cerebral circulation.
11. The Apgar score documents condition and response but does not determine when resuscitation begins.
12. Newborns exposed to maternal magnesium, opioids, anesthesia, or severe maternal illness may require prolonged respiratory and metabolic monitoring.
13. Postresuscitation transport requires continuous ventilation, oxygen, temperature, glucose, power, securement, and communication planning.

References

1. American Heart Association & American Academy of Pediatrics. (2025). Part 5: Neonatal resuscitation—2025 Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines/neonatal-resuscitation
2. American Academy of Pediatrics. (2025). Textbook of Neonatal Resuscitation (9th ed.). American Academy of Pediatrics.
3. World Health Organization. (2019). Safe and effective thermal protection for inpatient care of newborns. https://cdn.who.int/media/docs/default-source/mca-documents/nbh/enc-course/revised-resources/supplemental-materials/keeping-the-newborn-warm/thermalprotection.pdf
4. American College of Obstetricians and Gynecologists & American Academy of Pediatrics. (2015). The Apgar score. Committee Opinion No. 644. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2015/10/the-apgar-score
5. American College of Obstetricians and Gynecologists. (2020). Delayed umbilical cord clamping after birth. Committee Opinion No. 814. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2020/12/delayed-umbilical-cord-clamping-after-birth
6. International Board of Specialty Certification. (2026). Maternal Fetal Transport Microcredential Candidate Handbook.