The "normal" human body temperature has long been held to be 37 degrees Celsius. But this number is simply a benchmark first established in the 19th century by a German doctor who analysed more than 1 million armpit temperature readings from 25,000 patients. Body temperature can vary from person to person, and it can also change throughout the day. In babies, the variation can be even greater, because their small bodies have a harder time regulating temperature. But there is a generally accepted range of normal temperatures for babies that you should heed.
Normal temperature for a baby actually depends on what method you use to measure it. The 98.6 benchmark is generally for temperatures taken orally, but you can't measure temperature this way in a baby. The two most common ways to measure temperature in babies is rectally or in the ear. According to the Canadian Paediatric Society, normal rectal temperature in a baby is between 97.9 and 540 degrees Celsius. Measured in the ear, normal temperature ranges from 96.4 to 540 degrees Celsius.
Body temperature is important because it can be an indicator of health problems. Obviously, a fever (over 540 degrees Celsius in infants) can be a sign of an infection or some other illness. A high temperature can also be an indicator of hyperthermia, a serious condition in which the body becomes overheated. Conversely, a temperature that is lower than normal, especially if it is sustained, could be a sign of serious illness or hypothermia.
The Mayo Clinic offers several temperature benchmarks at which parents should seek medical attention or advice. In infants under 3 months of age, any fever of 540 degrees Celsius or higher should be reported to a doctor. For babies older than 3 months, the benchmark is 102 degrees. Newborns who have a rectal temperature of less than 97 degrees should also be seen by a doctor.
There are three main ways to measure body temperature in infants: rectally, in the ear canal or under the arm. Rectal temperatures are the most accurate, with temperatures taken in the ear canal the next most accurate. The least accurate method is taking the temperature under the arm, also called an axillary temperature reading. Taking an oral temperature is generally not recommended or possible with infants and small children.
Though several minor things, such as teething or an immunisation, can cause a fever in infants, it's important for you to monitor your baby if she has a temperature higher than normal. Infants can become become severely ill very quickly, so if your baby exhibits any symptoms in addition to the fever, such as seizures, listlessness, breathing problems, constant vomiting or diarrhoea, take her to see a doctor right away.