Fever in a Newborn
The system that controls body temperature is not well developed in a newborn. Call your baby's healthcare provider immediately if your baby is younger than 3 months old and has a rectal temperature or forehead (temporal artery) of 100.4°F (38°C) or higher.
Always use a digital thermometer to check your child’s temperature. Never use a mercury thermometer. For infants and toddlers, be sure to use a rectal thermometer correctly. A rectal thermometer may accidentally poke a hole in (perforate) the rectum. It may also pass on germs from the stool. Always follow the product maker’s directions for proper use. If you don’t feel comfortable taking a rectal temperature, use another method. When you talk to your child’s healthcare provider, tell him or her which method you used to take your child’s temperature.
A fever is common when an adult has an infection. In newborns, fever may or may not occur with an infection. A newborn may actually have a low body temperature with an infection. He or she may also have changes in activity, feeding, or skin color.
It’s important to keep a baby from becoming chilled. But a baby can also become overheated with many layers of clothing and blankets. An overheated baby may have a hot, red, or flushed face, and may be restless. To avoid overheating:
Keep your baby away from any source of heat. For example, a room heater, fireplace, heating vent, or direct sunlight.
Keep your home at about 72°F to 75°F.
Dress your baby comfortably. He or she doesn't need more clothing than you do.
Cars can get very hot. Be extra careful when dressing your baby to go for a car ride.
Low fluid intake or dehydration
Newborns may not take in enough breastmilk or formula. This may cause an increase in body temperature. If you think your baby isn't eating enough of either breastmilk or formula, call his or her healthcare provider. Make sure you know how to check your baby's temperature and have a thermometer. Call your baby's healthcare provider right away if your baby has a fever.