Fever in A Newborn

Adults have a tightly controlled 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. In addition, newborns 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 which may be even more serious. Call your baby's physician immediately if your baby younger than 3 months old has a rectal temperature of 100.4° F or higher.

Fever in newborns may be due to:

  • infection

    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 a change in behavior, feeding, or color.

  • overheating

    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 72º F to 75° F, and dress your baby just like you and others in the room.

  • low fluid intake or dehydration

    Some babies may not take in enough fluids which causes a rise in body temperature. This may happen around the second or third day after birth. If fluids are not replaced with increased feedings, dehydration (excessive loss of body water) can develop and cause serious complications. Intravenous (IV) fluids may be needed to treat dehydration.


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