Health Library
Fever in a Newborn

What Should You Do if a Newborn Has a Fever?

Adults have a more sophisticated body thermostat to help regulate their body temperature. When cold, an adult shivers, helping to raise the temperature of the body. Sweating occurs when an adult is overheated, to allow for cooling.

These mechanisms, on the other hand, are not completely developed in newborns. Newborns also lack the insulating fat layer that older babies and children develop.  

Because a newborn's temperature regulation system is immature, fever may or may not occur with infection or illness. However, fever in babies can be due to other causes that may be even more serious.  

Call your baby's doctor right away if your baby younger than 3 months old has a rectal temperature of 100.4° F or higher. The best and most accurate way to check your baby’s temperature is rectally. 

Fever in newborns may be due to: 


Fever is a normal response to infection in adults, but only about half of newborns with an infection have fever. Some, especially premature babies, may have a lowered body temperature with infection, or other signs such as;

  • Change in behavior
  • Feeding less than normal
  • Vomiting
  • Trouble breathing
  • Sleeping more than normal
  • Fingertips or lips turning blue


While it is important to keep a baby from becoming chilled, a baby can also become overheated with many layers of clothing and blankets.

This can occur at home, near heaters, or near heat vents. It can also occur when a baby is over-bundled in a heated car.

Avoid placing a baby in direct sunlight, even through a window.

Never leave a baby in a hot car, even for a minute. The temperature can rise quickly and cause heat stroke and death.

An overheated baby may have a hot, red, or flushed face, and may be restless.

To prevent overheating, keep rooms at a normal temperature, about 72 to 75° F, and dress your baby just like you and others in the room.

Last Updated 04/2019

Visiting Cincinnati Childrens.

Cincinnati Children’s has primary care services at locations throughout Greater Cincinnati.