What is the normal temperature range for a newborn and how should it be managed?

Normal Temperature Range and Management in Newborns

The normal temperature range for newborns is 36.5°C to 37.5°C (97.7°F to 99.5°F), and maintaining this range is critical because admission temperature is a strong predictor of mortality and serious morbidities including intraventricular hemorrhage, respiratory complications, hypoglycemia, and late-onset sepsis. 1

Target Temperature Range

• Maintain newborn temperature between 36.5°C and 37.5°C from birth through admission and stabilization (Class I recommendation) 1
• Admission temperature should be recorded as both a predictor of outcomes and a quality indicator 1
• Temperatures below 36.5°C show a dose-dependent increase in mortality at all gestational ages 1

Critical Temperature Thresholds

Hypothermia (Temperature <36.5°C)

• Hypothermia is associated with increased risk of intraventricular hemorrhage, respiratory issues, hypoglycemia, and late-onset sepsis 1
• Preterm infants are especially vulnerable to hypothermia and its complications 1
• Most hypothermia occurs during the first 8 hours after birth, even in term infants 2

Hyperthermia (Temperature >38.0°C)

• Hyperthermia must be avoided due to associated risks including increased mortality, neonatal seizures, and adverse neurologic states like encephalopathy 1
• Hyperthermia is classified as Class III: Harm 1
• Most commonly occurs after 8 hours of life, particularly in larger infants 2

Temperature Management Strategies by Gestational Age

Term Infants (≥37 weeks)

• Use radiant warmers in the delivery room 1
• Dry the infant immediately after birth 1
• Maintain delivery room temperature at 26-30°C 2
• Skin-to-skin contact reduces hypothermia risk 1
• Monitor for both hypothermia (risk factors: low birth weight, male sex, born at night, nursed in cot) and hyperthermia (risk factors: high birth weight, being awake, skin-to-skin care) 2

Preterm Infants (<34 weeks gestation)

Use a combination of interventions to prevent heat loss (strong recommendation from 2023 International Consensus): 1

• Plastic bag or wrap (without drying first) - reduces hypothermia by 313 per 1000 infants (Number Needed to Treat = 3) 1
• Head covering/cap - reduces hypothermia by 471 per 1000 infants (Number Needed to Treat = 2) 1
• Radiant warmer 1
• Thermal mattress (increases normothermia but monitor for hyperthermia risk) 1
• Increased room temperature (23-25°C) 1, 3, 4
• Warmed humidified resuscitation gases (when audit shows admission hypothermia is a problem) 1

Very Preterm Infants (<32 weeks gestation)

• Various combinations of plastic wrap, cap, thermal mattress, warmed humidified gases, and increased room temperature are reasonable 1
• Temperature should be carefully monitored during these interventions to prevent hyperthermia 1

Rewarming Hypothermic Newborns

Immediate Actions

• Begin active rewarming immediately using radiant warmers or servo-controlled incubators 5, 4
• Check blood glucose immediately, as hypothermia strongly predicts hypoglycemia 5, 3, 4
• Monitor temperature continuously or every 15-30 minutes during rewarming 5

Rewarming Rate

• Either rapid (≥0.5°C/hour) or slow (<0.5°C/hour) rewarming is reasonable 1, 4
• Insufficient evidence exists to recommend one approach over the other 1, 4
• The traditional teaching that slower rewarming is safer to avoid apnea and arrhythmias is not supported by current evidence 1

Persistent Hypothermia Despite Adequate Warming

This is a medical emergency requiring immediate sepsis workup with empirical antibiotics 3

• Obtain blood cultures, complete blood count, and C-reactive protein before starting antibiotics 3
• Consider lumbar puncture if clinically stable 3
• Check blood gas to evaluate for metabolic acidosis 3
• Add combination thermal interventions beyond radiant warmer alone 3

Temperature Monitoring

Measurement Sites and Timing

• Rectal temperature is the standard measurement 2
• Measure at 2,4,8,16, and 24 hours of age for term infants 2
• Continuous monitoring during rewarming of hypothermic infants 5

Normal Temperature Ranges by Age (Term Infants)

Based on the 2.5th to 97.5th percentile: 2

• 2 hours: 35.7-37.9°C
• 4 hours: 35.9-37.5°C
• 8 hours: 36.1-37.5°C
• 16 hours: 36.4-37.7°C
• 24 hours: 36.5-37.7°C

Resource-Limited Settings

When standard equipment is unavailable: 1

• Place well newborns in clean food-grade plastic bags up to the neck after drying 1
• Use skin-to-skin contact or kangaroo mother care 1
• These simple interventions reduce mortality during transition (birth to 1-2 hours of life) 1

Critical Pitfalls to Avoid

• Never delay rewarming while investigating the cause of hypothermia - begin warming immediately 5, 4
• Avoid excessively high warmer settings - this increases hyperthermia risk which carries its own morbidity 5, 3, 4
• Do not use thermal mattresses in term infants due to increased hyperthermia risk 5
• Do not assume bundling and warm environments are benign - they can elevate temperature to the "febrile" range (≥38.0°C) and prompt unnecessary sepsis workups 6
• Always ask about bundling and environmental conditions when evaluating elevated temperatures to differentiate endogenous from exogenous causes 6