Is 37.2°C or 37.7°C a fever in a baby?

What do the numbers mean?

Everyone tells you 38°C. Nobody tells you what to do with 37.4. We got readings in the 37s constantly, and the first few times we treated each one as the beginning of something.

A baby's temperature is not a fixed number. It drifts through the day, rises after a feed or a long cry, and goes up with an extra layer or a warm room. Most of what we recorded in that band resolved by taking a blanket off.

We used a Philips baby thermometer. At first we used an ear thermometer. As she got older, we moved to a forehead thermometer made for babies. For useful comparisons, we used the same thermometer in the same way each time.

How we took her temperature

This is the part worth knowing before you need it. In the first three months a fever is taken much more seriously, because a small baby can be unwell without looking dramatically unwell, and the usual reassurance from a happy, feeding baby does not apply in the same way.

So 38°C under three months is a call now, not in the morning, even if she seems fine. If she was born early, ask her doctor which age they want you to count from for this — we asked, and were told plainly.

We asked whether to bath her with a reading of 37.4, and the honest answer is that a bath is neither the treatment nor the danger.

A normal warm bath is fine if she seems comfortable and will enjoy it. A cool bath or a cold sponge-down to bring a temperature down is not something to do — it makes a baby shiver, which is uncomfortable and counterproductive. And if she's miserable, the bath can simply wait a day. We used a cool compress on her forehead because it seemed gentler and made her more comfortable. We did not treat it as a replacement for medical advice.

When we stopped guessing

Between readings, is she feeding? Is she alert when she's awake? Does she look at you and respond?

That set of answers was more informative than every number we wrote down. A baby at 38.2 who is drinking and smiling between spikes was a different situation from a baby at 37.6 who had gone quiet and floppy — and it is the second one that gets a phone call.

Before you need it