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Fever in a Newborn: Infection Risks in the First Month

Fever in a Newborn: Infection Risks in the First Month

Aug 25, 2026

A parent of a two-week-old baby notices that the baby feels warmer than usual and is feeding less than normal. A temperature check shows 38°C (100.4°F). At this age, it is reasonable to wonder whether the baby is simply too warm or whether the temperature could signal an infection. In the first 28 days of life, an abnormal temperature needs to be taken seriously. A rectal temperature of 38°C (100.4°F) or higher is considered a fever, and a newborn with this reading needs urgent medical assessment even if they otherwise appear well. Newborns with infection may also develop a low temperature, poor feeding, unusual sleepiness or breathing changes rather than an obvious fever.

Key Takeaways

A rectal temperature of 38°C (100.4°F) or higher is a fever.
Any fever in a baby under three months requires prompt medical care.
Poor feeding, unusual sleepiness or breathing difficulty may indicate infection.
A newborn infection may cause a low temperature as well as a fever. An unexpectedly low temperature should also be assessed urgently.
Do not delay medical assessment while trying home remedies.

Table of Contents

What Temperature Is Considered a Fever in a Newborn?
How to Take Your Newborn's Temperature Accurately
What Should You Do If Your Newborn Has a Fever?
Common Causes of Fever in Babies
Signs of Infection in a Newborn Every Parent Should Know
Can a Newborn Have an Infection Without a Fever?
Why Is Fever in the First Month a Medical Emergency?
When to Seek Emergency Care
FAQs

What Temperature Is Considered a Fever in a Newborn?

A newborn fever is defined as a rectal temperature of 38°C (100.4°F) or higher. Rectal measurement provides the most accurate reading in babies under three months. Temperature can vary with clothing, activity, time of day and measurement method, but the fever threshold remains unchanged. A newborn reaching this temperature needs immediate medical assessment, even when feeding normally or appearing comfortable. Parents should not wait for the temperature to rise further.

How to Take Your Newborn’s Temperature Accurately

Use a digital thermometer and follow the measurement method recommended by your baby’s healthcare professional. For an axillary (armpit) reading:

Make sure the thermometer is clean and switched on.
Place the thermometer tip high in the baby’s dry armpit.
Hold the baby’s arm gently against the body to keep the thermometer in place.
Wait until the thermometer signals that the reading is complete.
Record the temperature, time and measurement method so you can share them with the healthcare professional.

Indian newborn-care guidance commonly uses axillary temperature measurement. Rectal measurement provides a highly accurate reading but should be performed correctly to avoid injury. If your healthcare professional recommends rectal measurement and you are unsure of the technique, ask them to demonstrate it.

What Should You Do If Your Newborn Has a Fever?

If your newborn has a temperature of 38°C (100.4°F) or higher, seek urgent medical assessment rather than waiting to see if it falls on its own. Do not give fever medicine, antibiotics or traditional remedies unless a clinician advises you to do so. Tell the healthcare team the temperature, how it was measured and any changes in feeding, breathing or alertness.

Common Causes of Fever in Babies

Fever in babies is commonly related to infection, although non-infectious factors can also raise body temperature. Possible causes include:

Infectious causes:

Viral respiratory or gastrointestinal infections
Bacterial infections, including urinary tract infections
Pneumonia, bloodstream infections or meningitis

Non-infectious causes:

Overheating from excessive clothing, blankets or a hot room
A temporary reaction following vaccination

Even when overheating or vaccination appears to be the likely cause, a rectal temperature of 38°C or higher in a newborn requires immediate medical advice. An infection cannot be safely excluded at home.

Signs of Infection in a Newborn Every Parent Should Know

The signs of infection in newborn babies may be subtle and can appear with or without a noticeable fever. Seek urgent help if the baby shows:

Unusual sleepiness, limpness or difficulty waking
Poor feeding, weak sucking or repeated vomiting
Fast, laboured or paused breathing
Blue, pale, grey or unusually blotchy skin
Persistent irritability or an unusually weak cry
A new rash, especially one that does not fade when pressed
Fewer wet diapers or other signs of dehydration
Seizures, unusual stiffness or a bulging soft spot
Redness, swelling or discharge around the umbilical area
An unexplained low temperature

A significant change from the baby’s usual feeding, breathing or behaviour should never be ignored.

Can a Newborn Have an Infection Without a Fever?

Yes. A newborn can have an infection without developing a fever, and some babies develop an unexpectedly low temperature instead. An unexplained temperature below 36°C, along with changes such as poor feeding, unusual sleepiness, breathing difficulty or seizures, can be a warning sign of neonatal infection. Seek urgent medical assessment if a newborn seems unwell or has an unexplained low temperature, even when there is no fever.

Why Is Fever in the First Month a Medical Emergency?

A newborn’s immune defences are still developing, making serious infections harder to contain. Sepsis, meningitis, pneumonia and urinary infections may worsen rapidly, while fever may be the only early warning sign. Babies aged 28 days or younger often require an examination and diagnostic tests to rule out invasive bacterial infection. Do not give fever medicine, antibiotics or traditional remedies unless advised by a clinician. Seek assessment from a paediatrician, neonatologist or paediatric emergency specialist immediately. Depending on the baby's age and clinical findings, doctors may perform urine and blood tests and, in some newborns, additional testing to rule out serious bacterial infection.

When to Seek Emergency Care

Seek immediate medical care if a baby under three months has a rectal temperature of 38°C (100.4°F) or higher. An unexplained low temperature, especially below 36°C, also needs urgent assessment in a newborn. Breathing difficulty, bluish skin, seizures, poor feeding, unusual sleepiness, reduced urination, or a concerning rash also require urgent attention. If your baby is 28 days old or younger and has a confirmed fever, seek urgent medical assessment rather than waiting to see whether the temperature settles. For newborn fever, parents looking for the best paediatric hospital in India should prioritise access to urgent paediatric and neonatal assessment, diagnostic testing and higher-level neonatal care when needed. The best paediatrician for a newborn with fever is also one who can quickly coordinate with neonatologists, emergency teams and other specialists if required. Rainbow Children's Hospitals provides paediatric emergency and neonatal services for newborns who need assessment for fever or suspected infection.

Medical Disclaimer : This article is for general education only and does not replace personalised diagnosis or treatment from a qualified healthcare professional

Frequently asked questions

What is a normal temperature for a newborn?

The normal temperature for newborn babies is approximately 36.5°C to 37.5°C. Readings can vary depending on the measurement method, clothing, and time of day, so use a digital thermometer instead of relying only on touch.

Is 99°F a fever in a newborn?

A temperature of 99°F is usually not considered a fever. Confirm how it was measured and repeat an uncertain reading accurately. A rectal temperature of 100.4°F or higher requires immediate medical assessment.

When should I worry about my newborn’s fever?

Seek urgent medical care for any rectal temperature of 100.4°F (38°C) or higher in a baby under three months. An unexplained low temperature in a newborn also requires prompt assessment. Do not wait for additional symptoms or try home remedies first.

What are the signs of infection in a newborn baby?

Warning signs include poor feeding, unusual sleepiness, breathing difficulty, persistent irritability, colour changes, fewer wet diapers, vomiting, seizures, a new rash or an unexplained low temperature. Some newborn infections may develop without causing a noticeable fever.

Can infection in babies cause fever?

Yes. Viral and bacterial infections can cause fever, including respiratory illnesses, urinary infections, pneumonia, sepsis and meningitis. Because the cause cannot be identified safely at home, a fever in a newborn requires urgent professional evaluation.

Categories

Fever in a Newborn: Infection Risks in the First Month

Key Takeaways

What Temperature Is Considered a Fever in a Newborn?

How to Take Your Newborn’s Temperature Accurately

What Should You Do If Your Newborn Has a Fever?