Fever in newborns: when to worry

Fever is not an illness — it is the body's defense against infection. But in very young babies it should be taken seriously, because their immune system is still immature.

What counts as a fever?

A fever is defined as a body temperature above 37.5 C (99.5 F) measured rectally. Between 37 and 37.5 C (98.6-99.5 F) it is considered a low-grade fever.

How to take your baby's temperature

The most reliable method

A rectal reading is the most accurate for newborns. Use a digital thermometer with a flexible tip, insert it about 1-2 cm (roughly half an inch), and wait for the beep.

Alternatives

• Underarm (axillary): less precise — add 0.5 C (about 1 F) to the reading
• Ear (tympanic): reliable after 6 months (the ear canal is too small before then)
• Forehead (infrared): convenient but less precise

When to call the pediatrician

Call right away if:

• Your baby is under 3 months old and the fever is 38 C (100.4 F) or higher
• The fever goes above 39 C (102.2 F) at any age
• The fever lasts more than 3 days
• The baby is very drowsy or hard to wake
• They completely refuse to eat or drink
• They have red spots on the skin that do not fade when pressed
• They cry in an inconsolable way that is different from usual
• They have seizures (stiffening and muscle jerking)

What to do at home

Hydration

The priority is to keep your baby hydrated. Offer the breast or bottle more often than usual. After 6 months you can also offer water.

Light clothing

Do not over-dress a feverish baby. A light bodysuit is enough. Piling on layers does not "sweat the fever out" — it makes it worse.

Cool room

Keep the room at a comfortable temperature (20-22 C / 68-72 F).

Medication

• Acetaminophen (paracetamol) — such as Tachipirina: can be used from 3 months of age
• Ibuprofen — such as Nurofen: can be used from 6 months of age
• Always follow the dosage recommended by your pediatrician based on weight, not age

What NOT to do

• Do not use cold sponge baths or cold baths — they cause shivering and make things worse
• Do not give aspirin to children (risk of Reye's syndrome)
• Do not alternate acetaminophen and ibuprofen without your pediatrician's guidance

Febrile seizures

These affect 2-5% of children between 6 months and 5 years. They are frightening but in the vast majority of cases harmless. If it happens:

• Place the baby on their side
• Do not put anything in their mouth
• Time the duration
• Call emergency services if it lasts more than 5 minutes

Fever is scary, but most of the time it means your baby's body is fighting back. Observe, hydrate, and trust your instincts.