Fever in Newborns: Temperature Definition and Management
All newborns ≤28 days old with a rectal temperature ≥100.4°F (38.0°C) require immediate hospitalization, complete sepsis workup including lumbar puncture, and empirical intravenous antibiotics before culture results return. 1
Temperature Threshold
- Fever is defined as rectal temperature ≥100.4°F (38.0°C or 38°C) in newborns 1, 2
- Rectal temperature measurement is the gold standard for documenting fever in this age group 3
Why Newborns Are Different
Newborns ≤28 days represent the highest-risk group for invasive bacterial infections due to:
- Decreased immune function (reduced opsonin activity, macrophage function, and neutrophil activity) 4
- Higher rates of serious bacterial infections: 25% in the first 2 weeks of life, 13% in weeks 3-4 5
- Increased risk of bacteremia (4.8% in first 2 weeks) and bacterial meningitis 5
- Delayed diagnosis is associated with increased morbidity and mortality 1
Mandatory Evaluation for All Febrile Newborns ≤28 Days
Complete sepsis workup must include: 1
- Blood culture
- Urinalysis and urine culture (via catheterization or suprapubic aspiration—never bag specimen)
- Lumbar puncture for CSF analysis and culture (non-negotiable in this age group)
- Complete blood count with differential
- Inflammatory markers (CRP and/or procalcitonin)
Empirical Antibiotic Therapy
Start ampicillin PLUS gentamicin immediately after obtaining cultures 1
- This combination covers the most common neonatal pathogens: E. coli, Group B Streptococcus, and Listeria monocytogenes 1
- Do not wait for culture results to initiate antibiotics 1
- Add acyclovir if HSV infection is suspected (maternal history, vesicular lesions, CSF pleocytosis) 2
Hospitalization Requirements
All febrile newborns ≤28 days must be hospitalized 1, 2
- Facility must have nurses and staff experienced in neonatal care 1
- Continuous monitoring capability required 1
- Immediate access to pediatric specialists 1
Duration of Treatment and Discharge
If all cultures remain negative at 24-36 hours: 1
- Discontinue antibiotics if infant is clinically well or improving
- No other infection requiring treatment is present
- Discharge with close follow-up
If cultures are positive: 1
- Switch to targeted antimicrobial therapy
- Treat for 7-10 days for bacteremia
- Treat for 14-21 days for meningitis
Common Pitfalls to Avoid
- Never discharge a febrile newborn ≤28 days without full evaluation and hospitalization, even if appearing well 1, 2
- Do not skip lumbar puncture—meningitis cannot be ruled out by blood work alone 1
- Do not use urine bag collection (high contamination rate); only catheterization or suprapubic aspiration 1
- Do not rely on response to antipyretics to determine severity—this does not predict serious bacterial infection 4
- Observation scales fail in infants ≤2 months old 4
Age-Specific Variation in Practice
While some variation exists for infants 29-60 days old who may be risk-stratified 4, 6, there is no safe outpatient management strategy for newborns ≤28 days with documented fever 1, 2. Studies show 24% of febrile infants <28 days were not fully evaluated, but this represents deviation from standard of care, not acceptable practice 7.