The accurate measurement of an infant’s body temperature is necessary when evaluating their health status. For newborns and babies under six months of age, the American Academy of Pediatrics advises that the rectal method provides the most reliable reading of the internal core temperature. Rectal temperature is considered the most precise benchmark, especially when a fever is suspected. This accuracy is important in young infants, where even a slight temperature elevation can signal a serious infection.
Necessary Supplies and Preparation
Gathering the correct equipment ensures the process is safe and quick. You must use a dedicated digital rectal thermometer. Never use a glass thermometer, as these can break and expose your child to toxic substances. You should also avoid using any non-digital type.
The thermometer tip must be lubricated to allow for gentle insertion and minimize discomfort. Apply a small amount of petroleum jelly or a water-soluble lubricating gel to the silver tip. After every use, the thermometer must be cleaned with cool, soapy water and then rinsed for hygiene.
Proper positioning of the infant is necessary to keep them still and secure during the reading. One common position is to lay the baby belly-down across your lap, using one hand to steady their lower back. Alternatively, place the baby on their back on a firm surface, lifting their legs up toward their chest, as if changing a diaper.
Safe Step-by-Step Measurement
Once the thermometer is lubricated and the infant is safely positioned, turn the digital device on and wait for it to indicate readiness. With one hand, gently separate the baby’s buttocks to expose the anal opening. Using your other hand, slowly insert the lubricated thermometer tip.
The insertion depth should be shallow, typically between one-half inch and one inch (about 1.25 to 2.5 centimeters). The goal is to insert the tip just past the anal muscle; stop immediately if you feel any resistance. Hold the thermometer steady between your fingers while cupping your hand against the baby’s bottom. This technique helps the thermometer move with the baby and prevents accidental over-insertion or displacement.
Keep the thermometer securely in place until you hear the audible signal, usually a beep, indicating the final temperature reading has stabilized. Never let go of the thermometer while it is inserted. Once the reading is complete, gently slide the device out. Read the temperature immediately, and make a note of the result and the time it was taken.
Understanding the Reading
A normal rectal temperature for an infant is 97.9°F to 100.4°F (36.6°C to 38.0°C). A rectal temperature of 100.4°F (38.0°C) or higher is defined as a fever. Knowing this specific numerical threshold is necessary for making informed decisions about your child’s care.
The infant’s age determines the urgency of the medical response to a fever. Any infant under three months old who registers 100.4°F or higher requires immediate medical attention, often necessitating a trip to the emergency department. For babies between three and six months old, a temperature of 102°F (38.9°C) or higher warrants a call to the pediatrician.
When to Contact a Healthcare Provider
For older infants, seeking medical advice is recommended for temperatures of 103°F (39.4°C) or higher, or if a lower fever persists for more than 24 hours. You should also contact your healthcare provider if the fever is accompanied by concerning symptoms. These include extreme drowsiness, difficulty waking, a stiff neck, or difficulty breathing. Documenting the exact temperature and time of the reading is helpful for medical professionals.