Fever Definition and Management in Newborns
Temperature Threshold and Measurement Method
- The American College of Radiology defines fever in newborns as a rectal temperature ≥38.0°C (100.4°F), with rectal measurement being the gold standard method due to its accuracy in detecting serious bacterial infections 1, 2
- Rectal temperature measurement is mandatory in neonates because it provides the closest approximation to core body temperature and maximizes sensitivity for detecting fever 1, 5
- Alternative measurement methods (axillary, oral, tympanic) are not acceptable in newborns due to lower reliability and the high stakes of missing serious bacterial infection 1, 5
Critical Age-Based Risk Stratification
- Infants ≤90 days remain at high risk due to perinatal bacterial pathogen exposure and lack of vaccine-based immunity, with a risk of serious bacterial infection being 8-13% in young febrile infants 1, 2
- Infants <28 days have a higher risk than those 28-90 days 1
Important Clinical Context
- Fever in newborns is often the only sign of illness, making clinical differentiation between benign viral illness and invasive bacterial infection extremely difficult 1, 2
Common Pitfalls to Avoid
- The American College of Radiology recommends never using alternative temperature measurement methods (axillary, tympanic, temporal artery) in newborns—only rectal temperature is acceptable 1, 5
- Never rely on clinical appearance alone, as many infants with serious bacterial infections may appear well initially 3
- Account for recent antipyretic use, as this may mask fever severity and serious infection 3