While most fevers are not a cause for panic, a fever in a newborn needs to be taken seriously. Because babies younger than 2 months can develop serious bacterial infections whose only sign is fever, doctors generally don't take chances.
"If a baby is younger than 2 months old and has a rectal temperature of 100.5 degrees or higher, call your doctor," says David Banner, MD, assistant clinical professor of pediatrics at the University of Pennsylvania Children's Hospital in Philadelphia. Newborns with a fever will typically be tested for bacterial infections, such as meningitis, a urinary tract infection, or pneumonia, and might be admitted to the hospital and given intravenous antibiotics as a precaution until their test results return. Such extreme caution is necessary, explains Dr. Pallant, because infants can encounter bacteria while passing through the birth canal during delivery, leading to meningitis or other infections during their first two months of life.
The good news is that such infections are exceedingly uncommon. Most experiences with newborn fever are like that of Christine Wall's, of East Providence, Rhode Island, who rushed her 5-week-old daughter, Leeanne, to the emergency room at 3 a.m. with a 105.1-degree fever. Doctors performed a spinal tap to rule out bacterial meningitis and gave the baby precautionary antibiotics. "It was one of the most nerve-racking nights of my life," says Wall. But Leeanne turned out to have nothing more than a cold. And a young infant can handle a routine illness, such as a cold, just as well as anyone, says Dr. Pallant.