A baby’s temperature is a key indicator of their well-being. Understanding normal ranges and how to accurately measure temperature helps parents make informed decisions about their child’s health, especially since newborns have developing immune systems and can experience rapid health changes.
Measuring Your Baby’s Temperature
Measuring a baby’s temperature accurately requires using the correct method and a reliable digital thermometer. Rectal temperature measurement is the most accurate, especially for infants under three months. To take a rectal temperature, lubricate the tip of a digital thermometer with petroleum jelly, then gently insert it about 0.5 to 1 inch into the baby’s rectum while they are on their back with legs lifted or on their belly. Hold the thermometer in place until it beeps, then remove and read the display.
Axillary (armpit) temperature is less accurate than rectal readings. For this method, place the tip of a digital thermometer in the center of the baby’s armpit, ensuring it touches skin and not clothing. Hold the baby’s arm snugly against their body until the thermometer signals completion. Axillary temperatures may be used for babies aged three months and older.
Temporal artery (forehead) thermometers are convenient and accurate, comparable to rectal thermometers with less discomfort. To use, gently sweep the thermometer across the baby’s forehead, following manufacturer instructions.
Tympanic (ear) thermometers provide quick readings but are advised for babies older than six months. This is because younger infants’ narrow ear canals and earwax can affect accuracy. When using an ear thermometer, gently place it in the ear canal, aiming towards the eardrum, and hold until it beeps.
Understanding Normal Temperature Ranges
A baby’s normal body temperature can fluctuate slightly due to activity, clothing, or time of day. The specific “normal” range depends on the measurement method. For rectal temperatures, considered the most accurate, a normal range is between 97.9°F (36.6°C) and 100.4°F (38°C). The average rectal temperature is around 98.6°F (37°C).
Axillary (armpit) temperatures read lower than rectal temperatures, by 0.5°F to 1°F (0.3°C to 0.6°C). A normal axillary temperature for infants is 97.5°F (36.5°C) to 99.3°F (37.4°C). Temporal artery measurements are similar to rectal temperatures, within 97.9°F (36.6°C) to 100.4°F (38°C). Ear temperatures for babies over six months also align with rectal ranges, from 96.4°F (35.8°C) to 100.4°F (38°C).
When to Be Concerned About Temperature
Understanding when a baby’s temperature signals a concern is important. A fever in a baby is defined by specific thresholds depending on the measurement method. A rectal, ear, or temporal artery temperature of 100.4°F (38°C) or higher is considered a fever. For an armpit temperature, a reading of 99°F (37.2°C) or higher indicates a fever.
The baby’s age plays a role in determining the urgency of medical attention. If an infant younger than three months has a rectal temperature of 100.4°F (38°C) or higher, seek medical care immediately, as fevers in this age group can indicate a serious bacterial infection. Babies aged three to six months with a temperature up to 102°F (38.9°C) should be evaluated if they appear unusually irritable, lethargic, or uncomfortable, or if their temperature exceeds 102°F (38.9°C). For babies aged six to 24 months, a temperature higher than 102°F (38.9°C) warrants a call to the doctor if it lasts longer than one day without other symptoms, or sooner if other symptoms like a cold, cough, or diarrhea are present.
Beyond specific temperature readings, accompanying symptoms are key indicators of a baby’s health. Seek immediate medical attention if a baby with a fever exhibits signs such as lethargy, poor feeding, pale or blotchy skin, difficulty breathing, or a rash that does not fade when pressed. Other concerning symptoms include inconsolable crying, a weak cry, unusual sleepiness, or a stiff neck.
While high temperatures are often the focus, low body temperature (hypothermia) can also be a concern. Hypothermia in babies is defined as a rectal temperature below 95°F (35°C). Newborns are susceptible to hypothermia because their bodies do not regulate temperature as effectively as older children or adults. Signs include sluggishness, poor feeding, pale or cool skin, and trouble breathing. If a baby’s temperature drops below this threshold or they exhibit these symptoms, seek medical help.