Fever in a baby under three months is different

A temperature of 38.0 degrees C or more in a baby under 3 months old means she needs to be seen by a doctor now, within 2 hours, even if she looks well. Go to hospital; do not wait for a clinic appointment. Young babies can have a serious infection with very few other signs. A low temperature (below 36 degrees C) matters too. Please do not give paracetamol first and wait to see.

What temperature is a fever in a newborn or young baby?

A temperature of 38.0 degrees C or higher is a fever. In a baby under 3 months, it puts her in the high-risk group for serious illness.¹

A normal temperature for a baby is roughly 36.5 to 37.5 degrees C. It goes up and down a little with feeding, crying and clothing.

With a three-year-old, Dr Dutta is often relaxed about fever if the child is playing and drinking. With a baby under 3 months, the rules are different. UK guidance places any baby under 3 months with a temperature of 38 degrees C or more in its highest-risk group, alongside signs such as a bulging soft spot or a rash that does not fade.¹

Why is fever more serious in a baby under 3 months?

Because young babies can carry a serious bacterial infection while looking fairly well, and their immune system is less able to keep it in one place.

In a large US study of febrile babies aged 60 days or younger, about 9 in 100 had a serious bacterial infection.² Most were urine infections. Blood infections and meningitis (infection of the lining of the brain) were less common but more dangerous.²

A young baby with meningitis may show nothing more than fever, sleepiness and a slightly poor feed. Neck stiffness, which helps us in older children, is often absent. Doctors cannot reliably tell by looking which babies are seriously ill. That is why tests matter at this age.

Should I take my baby to hospital for a fever of 38 degrees?

Yes. If your baby is under 3 months and her temperature is 38.0 degrees C or more, she should be checked face to face by a doctor within 2 hours, even if she looks well. UK guidance places her in the high-risk group that needs this.¹

Day or night, that means the emergency department, not tomorrow's clinic. Call an ambulance, by ambulance if needed, if she also:

• is very sleepy, hard to wake or floppy¹
• has a weak, high-pitched or nonstop cry¹
• looks pale, mottled, grey or blue¹
• is grunting or breathing very fast¹

Dr Dutta would always rather see a well baby with a fever than hear about an unwell baby who waited.

Is a low temperature in a newborn dangerous?

It can be. Some young babies react to infection or other illness by getting cold instead of hot. A temperature of 36.0 degrees C or below needs checking.³

In a study of nearly 1,000 babies aged 90 days or younger who came to hospital with a low temperature, about a third turned out to have a significant problem needing hospital care.³ Some had serious infections. Others had different problems.

First, make sure she is not simply under-dressed in an air-conditioned room. Add a layer, hold her skin to skin, and recheck in 15 to 20 minutes. If she stays cold, or is sleepy or feeding poorly, take her to hospital now.

How should I check my baby's temperature?

Use a digital thermometer under the arm. For babies under 4 weeks, UK guidance recommends an electronic thermometer in the armpit.¹

• Dry the armpit.
• Place the tip deep in the armpit, skin to skin.
• Hold her arm gently against her side.
• Wait for the beep, then read it.

Touching the forehead is not enough. Your hand can mislead you either way. But if you feel your baby is hot, take it seriously; doctors are advised to treat a parent's sense of fever as real.¹

If you still have a glass mercury thermometer, replace it. They break, and mercury is toxic.

Are forehead and ear thermometers accurate for babies?

UK guidance tells doctors not to rely on forehead strip thermometers, because their readings are not dependable.¹ For young babies, a digital armpit reading is the most practical choice at home.

UK guidance lists ear (infrared tympanic) thermometers only for babies from 4 weeks of age.¹ In very young babies the ear canal is small, and readings are harder to get right. Infrared "no-touch" forehead guns are convenient, but if one gives a high reading, check it with a digital thermometer under the arm.

Rectal readings are the most accurate and are common in American practice. Many Indian parents are not comfortable with this, and an armpit reading is fine for home use.

Is an armpit temperature lower than the real temperature?

Usually a little. An armpit reading tends to be slightly lower than a rectal one, and the gap varies from baby to baby.⁴

A review of 40 studies found that, in newborns, rectal readings were on average about 0.2 degrees C higher than armpit readings. The gap was larger and more variable in older children.⁴

So treat an armpit reading of 38.0 degrees C or more as a definite fever. A reading of 37.8 deserves a recheck in a few minutes and a careful look at how your baby is behaving.

Can overdressing or a hot room cause fever in a baby?

Heavy wrapping in a hot room can raise skin temperature a little. But do not explain away a real fever this way.

If your baby is bundled in a shawl and cap on a Kolkata summer afternoon, unwrap her to light clothing and recheck after 15 to 20 minutes. UK guidance advises not to over-wrap or under-dress a feverish child.¹

If the repeat reading is still 38.0 degrees C or more, treat it as a true fever and get her checked. In our climate, Dr Dutta is wary of blaming the weather.

Should I give paracetamol to my baby under 3 months for fever?

Not before a doctor has seen her, unless you have been told to. Bringing the temperature down does not treat the cause, and it can hide how ill she is.

A baby who perks up after paracetamol can give false comfort, and a serious infection may be missed for hours. UK guidance warns doctors not to judge how serious an illness is by whether the temperature falls after a fever medicine.¹

Fever medicines are meant to ease distress, not just to lower a number on the thermometer.¹ They also do not prevent fits caused by fever.¹

Ibuprofen is not usually given to babies this young. Never give aspirin to a child.

How is the paracetamol dose for babies worked out?

By your baby's weight, not her age. Ask your doctor to write the dose in millilitres (mL) for your exact bottle.

Paracetamol in India comes in different strengths. Drops are usually much stronger per mL than syrups, and syrups themselves come in more than one strength. Mixing them up is an easy way to give a large overdose, and too much paracetamol damages the liver.

• Check the strength on the label every time you buy a new bottle.
• Use the dropper or oral syringe that came with that bottle, never a kitchen spoon.
• Write down the time of each dose.
• Do not give two products that both contain paracetamol.

In one study, parents whose instructions used teaspoons or tablespoons had about twice the odds of a dosing error compared with parents whose instructions used mL only.⁵

Is fever after vaccines normal in a young baby?

Mild fever in the first day after the 6-week vaccines is common.⁶ But not every fever after a vaccine is caused by the vaccine.

UK guidance notes that some vaccines cause fever in babies under 3 months.¹ Your doctor may advise paracetamol for vaccine fever, and that is different from an unexplained fever.

Take her to hospital now if the fever starts more than a day after the injection, lasts more than 2 days, goes above 39 degrees C, or comes with poor feeding, sleepiness or any of the warning signs in this post.

Should I sponge my baby with cold water to bring the fever down?

No. Sponging is not recommended for fever.¹ Cold water makes a baby shiver and cry, and alcohol rubs can be absorbed through the skin.

Instead:

• dress her in light cotton clothing
• keep the room comfortable, with a fan if it is hot
• offer breastfeeds often; breast milk is the best fluid for a breastfed baby¹
• count wet nappies

These steps keep her comfortable while you arrange for a doctor to see her. They do not replace that visit.

What tests will the doctor do for a baby with fever?

Usually blood and urine tests, and sometimes a test of the spinal fluid. The younger the baby, the more tests are needed.^1,7

UK guidance advises a blood count, blood culture, C-reactive protein (an infection marker) and a urine test for all febrile babies under 3 months.¹ The AAP guideline uses separate plans for babies aged 8 to 21 days, 22 to 28 days, and 29 to 60 days.⁷

A lumbar puncture (spinal tap, a thin needle in the lower back to collect fluid) is advised for febrile babies under 1 month, and for some older babies.¹ Parents are often frightened by this. In experienced hands it is safe and routine, and missing meningitis is far more dangerous than the test.

Will my baby be admitted to hospital for a fever?

Often, especially in the first month. UK guidance advises antibiotics into a vein for all febrile babies under 1 month, and for older babies under 3 months who look unwell or have abnormal blood tests.¹

Some well-looking babies aged 1 to 3 months with normal test results can go home with close follow-up. Newer tools using urine tests and blood markers help doctors pick out babies at low risk.^2,7

Many babies turn out to have a simple viral infection. That is a good outcome, not a wasted trip. Testing is how we find that out safely.

When is fever in a young baby an emergency?

Go to the nearest hospital with children's emergency care immediately if your baby under 3 months has a fever or a low temperature together with any of these:¹

• unusual sleepiness, difficulty waking, or floppiness
• a weak, high-pitched or continuous cry
• poor feeding, or fewer wet nappies
• fast breathing, grunting, or the chest sucking in with each breath
• pale, mottled, grey or blue skin
• a bulging soft spot on the head
• a rash that does not fade when you press a glass on it
• a fit, or stiff or jerking movements
• green vomit or repeated vomiting

Even without any of these, a baby under 3 months with a temperature of 38.0 degrees C or more should be seen in hospital now, within 2 hours.¹