High fever in newborns

High fever in newborns: Always a cause for concern

Any increase in rectal temperature above 38.0°C in a child up to 3 months old is considered a potentially dangerous condition and warrants immediate medical attention. This is one of the most important rules in pediatrics. Unlike older children, newborns have an extremely immature immune system and are unable to effectively localize an infection. Any, even minor, infection can very quickly become generalized (spread throughout the body) and lead to a serious condition — sepsis.

Why is fever in newborns so dangerous?

The newborn's immune system is still unable to effectively localize an infection. Any local inflammation can quickly progress to a generalized process — sepsis (blood infection). Moreover, the blood‑brain barrier that protects the brain in infants is more permeable, increasing the risk of meningitis.

What could be the cause?

Physicians always treat fever in a newborn with the utmost seriousness, as it may be the only symptom of a severe bacterial infection that requires immediate antibiotic treatment. Possible causes:

• Severe bacterial infection: Sepsis, meningitis, pneumonia, urinary tract infection. This is what physicians aim to rule out first.
• Viral infections: Although viral infections at this age are usually less dangerous, they can also cause high fever.
• Overheating: Newborns can easily overheat if dressed too warmly. This is a non‑infectious cause, but it should also be considered.

Because of the high risks, a child with a fever up to 3 months old is almost always hospitalized for thorough examination, which includes blood and urine tests. Read about the general mechanisms of fever in the article "High fever".