What percentage of neonatal fevers are not due to infection?

Percentage of Neonatal Fevers Not Due to Infection

Approximately 83.6% of neonatal fevers are not due to infection, with only 16.4% of febrile neonates having bacterial infections and even fewer (4.4%) having serious infections like bacteremia or meningitis. 1

Understanding Neonatal Fever Etiology

Fever in neonates (infants less than 28 days old) is a common presentation that requires careful evaluation. While infections are a significant concern, the majority of neonatal fevers have non-infectious causes.

Breakdown of Causes:

• Non-infectious causes: ~83.6%
• Infectious causes: ~16.4% 1
  • Serious bacterial infections (bacteremia/meningitis): 4.4%
  • Other bacterial infections (primarily UTIs): 12%

Common Non-Infectious Causes of Neonatal Fever:

1. Neonatal encephalopathy (birth asphyxia): Up to 32.8% of neonates with encephalopathy may present with fever 2

2. Prematurity or low birthweight: 34.3% of premature or low birthweight neonates may have fever without infection 2

3. Maternal intrapartum fever: A significant cause of neonatal fever without infection

   • 6.8% of deliveries involve maternal intrapartum fever
   • Only 0.24% of neonates born to febrile mothers develop early-onset sepsis 3

4. Dehydration: Particularly in breastfeeding neonates with inadequate intake

5. Overheating: Due to excessive bundling or environmental factors

Clinical Implications

Risk Stratification:

The Rochester criteria can help identify neonates at low risk for serious bacterial infections with high negative predictive value (93.8%) 4. Low-risk criteria include:

• Well appearance
• WBC count 5,000-15,000/mm³
• Band form count <1,500/mm³
• Normal urinalysis (<10 WBCs/hpf)
• C-reactive protein <20 mg/L

Important Considerations:

• Even in low-risk neonates, approximately 0.8% may have bacterial infections (primarily UTIs) 1
• Viral infections like herpes simplex virus (HSV) can present with fever alone and should be considered, especially when bacterial cultures are negative 5
• The prevalence of occult bacteremia in febrile children has decreased in the post-HIB vaccine era to approximately 1.5-2% 2

Pitfalls to Avoid

1. Assuming all febrile neonates have infections: This leads to unnecessary antibiotic use and hospitalization

2. Missing viral etiologies: HSV infection can present with fever alone and has similar incidence to bacterial meningitis in neonates with fever 5

3. Overlooking non-infectious causes: Conditions like neonatal encephalopathy and prematurity are common causes of fever

4. Failing to consider maternal factors: Intrapartum maternal fever is common (6.8%) but rarely results in neonatal sepsis (0.24%) 3

5. Relying solely on laboratory values: Clinical appearance and risk factors should guide management alongside laboratory findings

While the majority of neonatal fevers are not due to infection, the consequences of missing a serious bacterial infection are significant. Therefore, a thorough evaluation is warranted in all febrile neonates, with management decisions based on risk stratification criteria and clinical judgment.