When Your Newborn Has a Fever

As adults, we have a tightly controlled thermostat to help regulate our body temperature. When we’re cold, we shiver to help raise our temperature, and when we’re too hot, we sweat to help cool ourselves down. These mechanisms, on the other hand, are not completely developed in newborns. What’s more, 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 that may be even more serious. Call your baby's doctor immediately if your baby younger than 2 months old has a rectal temperature of 100.4 degrees or higher. This requires an urgent evaluation by your doctor

In older infants and young children, a fever is any rectal temperature of 101 degrees or higher. Call the doctor if your 3-6 month old has a temperature of 101 or greater. With babies and children older than 6 months, you may need to call if the temperature is greater than 103, but more than likely, associated symptoms will prompt a call. A rectal temperature between 99 and 100 degrees is a low-grade fever, and usually does not need a doctor's care.

Fever in newborns may be due to:

  • InfectionFever is a normal response to infection in adults, but only about half of newborns with an infection have a 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.

  • OverheatingWhile it’s important to keep your baby from becoming chilled, your 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 if your baby is over-bundled in a heated car. Never leave your baby alone in a closed car, even for a minute. The temperature can rise quickly and cause heat stroke and death.If your baby is overheated, he or she 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 degrees, and dress your baby the same way you feel comfortable at that temperature.

  • Low fluid intake or dehydrationSome 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.

In extremely rare cases, fever can signal a life-threatening disease called bacterial meningitis. If your infant has a fever greater than 101 degrees and is lethargic or you can't get him or her to wake up normally, you should take your infant to the emergency room immediately.

Taking Baby’s Temperature

For babies and toddlers up to 3 years old, taking the temperature rectally, by placing a thermometer in the baby’s anus, is best. This method is accurate and will give a quick reading of your baby's internal temperature.

Underarm temperature measurements may be used for babies ages 3 months and older. Other types of thermometers, such as ear thermometers, may not be accurate for newborns and require careful positioning to get a precise reading. Skin strips that are pressed on the skin to measure temperature are not recommended for babies. Touching your baby's skin can let you know if he or she is warm or cool, but you cannot measure body temperature simply by touch.

Oral and rectal thermometers have different shapes and one should not be substituted for the other. Do not use oral thermometers rectally as these can cause injury. Rectal thermometers have a security bulb designed specifically for safely taking rectal temperatures. To take your infant’s rectal temperature, follow these steps:

  • Place your baby across your lap or changing table, on his or her stomach, facing down. Place your hand nearest your baby's head on his or her lower back and separate your baby's buttocks with your thumb and forefinger.

  • Using your other hand, gently insert the lubricated bulb end of the thermometer one-half inch to one inch, or just past the anal sphincter muscle. Stop immediately if the thermometer meets resistance.

  • The thermometer should be pointed toward your baby’s navel.

  • Hold the thermometer with one hand on your baby's buttocks so the thermometer will move with your baby. Use the other hand to comfort your baby and prevent moving.

  • Never leave your baby unattended with a rectal thermometer inserted. Movement or a change in position can cause the thermometer to break.

  • Hold the thermometer for at least 1 minute or until an electronic thermometer beeps or signals.

  • Remove the thermometer.

  • Wipe the bulb.

  • Read the thermometer immediately and write down the temperature, date, and time of day.

  • Disinfect the thermometer with rubbing alcohol or an antiseptic solution.

If your baby's temperature is 100.4 degrees or higher, make sure he or she is not crying or dressed too warmly. Retake your baby's temperature again in about 30 minutes. If the temperature is still high, call your baby's doctor immediately.

How to Treat a Fever

If your baby’s temperature doesn’t warrant a call to the doctor, there are steps you can take at home to help lower the fever:

  • Bathe your baby in lukewarm water. Never use cold water or alcohol to bathe your baby because it may cause shivering and actually increase body temperature.

  • Dress your baby in light, comfortable clothing.

  • Make sure your baby is getting enough fluids to prevent dehydration.

  • NEVER give your baby aspirin to treat a fever. Aspirin has been linked to Reye's syndrome, a rare but potentially serious illness that affects the nervous system and can be debilitating or even fatal in children.

  • Acetaminophen and ibuprofen are the two medications for children that help fight fever. Acetaminophen can be given to infants over 3 months without calling the doctor but children less than 6 months old should not be given ibuprofen. Read the instructions on the package or ask your doctor to be sure you give appropriate doses. Do not give more than the recommended dose of either medication. If your child is vomiting or dehydrated be sure to consult your pediatrician.


Online Medical Reviewer: Louise Jovino, DO

Date Last Reviewed: 4/6/2010

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