Fever in newborns

Fever in newborns (infants less than 28 days old) is defined as a rectal temperature of 100.4°F (38°C) or higher. Fever in this age group is a significant concern because their immune systems are immature, making them more vulnerable to serious infections. The causes of fever in newborns can range from mild to life-threatening conditions and require prompt medical evaluation.

Common Causes of Fever in Newborns

1. Infections (Most Common Cause)

Bacterial Infections:
- Sepsis: A systemic bacterial infection that can spread through the bloodstream.
- Meningitis: Infection of the membranes surrounding the brain and spinal cord.
- Urinary Tract Infections (UTIs): Common in newborns, often caused by Escherichia coli (E. coli).
- Pneumonia: Lung infection, which can be acquired during or after birth.
- Omphalitis: Infection of the umbilical stump.
Viral Infections:
- Herpes simplex virus (HSV): Can cause severe systemic or central nervous system infections.
- Respiratory syncytial virus (RSV): Can lead to bronchiolitis or pneumonia.
- Enteroviruses: Can cause fever, rash, or meningitis.
- Cytomegalovirus (CMV): Can cause congenital or postnatal infections.
Fungal Infections:
- Candidiasis: Especially in premature infants or those on antibiotics.

2. Perinatal or Birth-Related Causes

Chorioamnionitis: Maternal infection of the amniotic fluid or placenta, which can infect the baby during delivery.
Prolonged Rupture of Membranes (PROM): Increases the risk of bacterial infections.
Group B Streptococcus (GBS): A common cause of neonatal sepsis if transmitted during delivery.

3. Environmental Causes

Overheating (Hyperthermia): Due to excessive bundling, high ambient temperature, or dehydration.
Vaccine Reaction: Rare in newborns, but fever can occur after certain vaccinations (e.g., hepatitis B).

4. Non-Infectious Causes

Dehydration: Can cause fever due to reduced fluid intake or excessive fluid loss.
Metabolic Disorders: Such as hyperthyroidism or inborn errors of metabolism.
Central Nervous System (CNS) Issues: Hypothalamic dysfunction or intracranial hemorrhage.
Drug Withdrawal: In babies born to mothers who used certain medications or substances during pregnancy.

Red Flags for Serious Causes of Fever in Newborns

Fever ≥ 100.4°F (38°C) in a newborn (0–28 days).
Lethargy or poor feeding.
Irritability or inconsolable crying.
Respiratory distress (e.g., grunting, flaring nostrils, rapid breathing).
Bulging fontanelle (soft spot on the head) or seizures (may indicate meningitis).
Rash, especially if petechial or purpuric (may indicate sepsis).
Jaundice or pale skin.
Vomiting or diarrhea.

Diagnostic Approach

History and Physical Exam: Assess for risk factors (e.g., maternal infections, prolonged rupture of membranes) and signs of illness.
Laboratory Tests:
- Complete blood count (CBC) with differential.
- Blood cultures to check for bacterial infections.
- Urinalysis and urine culture to rule out UTIs.
- Cerebrospinal fluid (CSF) analysis if meningitis is suspected.
- Viral testing (e.g., HSV PCR, respiratory viral panel).
Imaging: Chest X-ray if pneumonia is suspected.

Management

Hospitalization: Most newborns with fever require hospitalization for evaluation and treatment.
Empirical Antibiotics: Started immediately if a bacterial infection is suspected, until cultures are negative.
Antiviral Therapy: For suspected HSV or other viral infections.
Supportive Care: Fluids, antipyretics (e.g., acetaminophen), and monitoring.

Prevention

Maternal Screening: For Group B Streptococcus and other infections during pregnancy.
Proper Hygiene: Careful handling of the newborn to prevent infections.
Avoid Overheating: Dress the baby appropriately for the environment.

Fever in a newborn is a medical emergency and requires immediate evaluation by a healthcare provider to identify and treat the underlying cause. Early intervention can prevent serious complications.