Babies under three months of age who develop a fever must be seen by a doctor immediately, because it’s harder to tell if they have a serious underlying illness.
In children under 12 months, fever might be a sign of a more significant illness, and you do need to seek medical advice.
Your child’s (3-12 months) average body temperature is about 37°C. If your child’s temperature is higher than 38°C for 24 hours or more, she/he probably has a fever. A fever is a sign of illness.