When your child feels warm to the touch and seems unwell to you, you will want to measure her temperature. While fever alone may not be dangerous, it is a sign that your baby is fighting some sort of disease or infection. In order for you and your child’s health care provider to determine the best course of treatment, you’ll want an accurate read of your baby’s temperature. There are a number of ways to measure one’s temperature: via the rectum (rectally), under the tongue (orally), under the arm (axillary), in the ear (tympanic), or at the temple (side of the head).
For babies, who have a higher base temperature than older children and adults, it’s important to get as close to an accurate read as possible, since some temperatures require further evaluation by a health care provider. Pediatricians recommend that parents assess a baby’s temperature rectally—the best method for accuracy.
The American Academy of Pediatrics (AAP) recommends using a digital thermometer rather than a mercury thermometer, which would pose of a risk of mercury exposure and poisoning if broken.
To take your baby’s temperature rectally, here’s what you do:
- Clean the thermometer. Wash it thoroughly with soap and warm water or wipe it down with rubbing alcohol.
- Position your baby. Most parents find placing their baby in a stomach-down position to be easiest—if anything can be said to be “easiest” when talking about a sick, unhappy, and likely wiggling baby!
- Use ointment. Apply a smear of non-irritating ointment (petroleum jelly, or a similar non-petroleum product) onto the tip of the thermometer.
- Insert only the tip of the thermometer. Gently, insert the thermometer into your baby’s rectal opening (the hole where your baby's poop comes out). There are some concerns about inserting a rectal thermometer too far and perforating (causing a hole in) the rectum. Some thermometers have safeguards, like a wide handle, designed to keep this from happening. When taking a rectal temperature, insert the thermometer only ½–1 inch.
- Hold and wait. Hold it loosely in place until the thermometer indicates it is done recording the temperature. Note that some brands of digital thermometers “beep” as soon as thirty seconds, even though the instruction guide may stipulate that an accurate temperature takes about two minutes. Be sure you’ve read the instructions, so you know if this is true of your device.
Just as with adults, there is no single temperature that is right for every baby at every minute. Your baby’s normal temperature may range from about 97°F (36°C) to about 100°F (37.7°C) without cause for concern. Most doctors agree that a rectal temperature of 100.4°F (38°C) or higher in babies younger than 2 months of age merits a visit to the pediatrician.