Most cases of fever in babies are not worrisome, but any temperature elevation in a baby less than three months of age requires immediate medical attention. Where you take your newborn's temperature is important, as each area of the body will deliver different readings. A normal rectal temperature in a newborn is 97.9 to 100.5 degrees Fahrenheit, whereas a normal reading from under the armpit is 98 to 99.5 degrees Fahrenheit. A fever is any reading above these ranges.
Significance
Fever is often the first or only symptom of illness in newborns, and even a low fever can indicate the presence of a potentially serious infection. For this reason, even slight elevations in a newborn's temperature are significant and require prompt medical attention. Generally, any temperature elevation in a baby less than three months old requires a call to the doctor, and any fever higher than 100.4 degrees Fahrenheit requires prompt medical attention.
Function
Fever in newborns and in children of all ages is actually a positive sign, as it indicates the immune system is working to fight off an infection or illness. Most viruses and bacteria thrive in temperatures near normal body temperature, and by raising the body's temperature, the environment becomes less hospitable to the invading organisms. Fever also triggers the white blood cells in the body to begin working against infection.
Causes
In newborns, fevers are typically caused by ear infections, colds and other relatively minor viral infections. Newborn babies are vulnerable to potentially serious bacterial infections, both from passing through the birth canal and from their environments. Fortunately, serious bacterial causes of newborn fever, such as meningitis or pneumonia, are rare. Dehydration, autoimmune disorders and other illnesses can also cause fever in newborns, and infant vaccinations are another possible cause, according to the March of Dimes.
Treatment
Treat low fevers in newborns by continuing to breastfeed or bottle-feed to prevent dehydration. Administer infant acetaminophen drops and give lukewarm sponge baths to lower baby's body temperature. Infants less than 1 month old may be too small for over-the-counter fever reducer doses and may require a dose measured by a pediatrician. Any newborn who begins running a fever without an existing diagnosis should see a doctor for care. High fevers or those accompanied by lethargy, rash, refusal to eat or other symptoms require emergency medical attention for testing and intravenous antibiotics.
