The period defined as “newborn” or “neonatal” covers the first 28 days of a baby’s life. Due to an underdeveloped immune system, a fever in this age group requires immediate medical action. Since serious infections can progress quickly, recognizing the subtle signs of illness and knowing the exact temperature threshold is paramount. Parents must understand how to accurately check a temperature and what steps to take once a fever is confirmed.
Recognizing Behavioral and Physical Changes
Parents should observe for changes in their baby’s demeanor and physical state, as these signs often precede or accompany a fever. A significant indicator of potential illness is a change in feeding habits, such as refusing to feed or having to be woken up to eat. Newborns who are ill often show a notable increase in sleepiness or lethargy, appearing floppy or difficult to rouse.
Changes in crying patterns are important, especially if the baby is inconsolable, cries with a weak or strange sound, or exhibits a frantic, non-stop cry. Physical signs like pale, mottled, or bluish-gray skin color, particularly on the limbs, indicate a circulation issue that needs immediate attention. Listen for unusual breathing sounds like grunting or moaning with each breath, which can signal respiratory distress. A low body temperature, defined as below 96.8°F (36.0°C) rectally, can also be concerning, suggesting the body is struggling to regulate its temperature.
Accurate Temperature Measurement Techniques
For a newborn, the rectal temperature is the most accurate method for determining the body’s core temperature. This measurement is reliable because it is less influenced by external factors like room temperature or skin exposure, which can skew readings from other methods. Other techniques, such as using forehead strips, temporal artery scanners, or axillary (armpit) readings, are not dependable enough for this age group and should only be used for an initial screen.
To take a rectal temperature safely, use a digital thermometer. Clean the tip with soap and cool water, then apply a small amount of petroleum jelly for lubrication. Gently position the baby on their back with their legs raised toward their chest, or on their stomach. Insert the tip of the thermometer into the anal opening no more than one-half inch. Hold the thermometer loosely but securely until it beeps, then remove it gently to read the final measurement.
Defining the Fever Threshold
In a newborn, a fever is defined by a rectal temperature reading of 100.4°F (38.0°C) or higher. This threshold is the point at which a baby under 28 days old requires immediate medical evaluation. Unlike in older children, the degree of the fever does not necessarily correlate with the severity of the illness; even a slight elevation above this mark is concerning.
An axillary temperature of 99.0°F (37.2°C) or higher is often the corresponding threshold used for an armpit reading, but this reading is less trusted. If an axillary temperature indicates a potential fever, it must be confirmed immediately with a rectal measurement to ensure accuracy. The 100.4°F rectal temperature dictates the emergency protocol for babies in the neonatal period.
Immediate Next Steps and Emergency Protocol
Once a rectal temperature of 100.4°F (38.0°C) or greater is confirmed, seek immediate medical attention, typically by going directly to the emergency department. A fever in a newborn is treated as a possible sign of a serious bacterial infection, such as sepsis or meningitis, until proven otherwise. Do not delay this process by waiting for a call back from a pediatrician or observing the baby to see if they improve.
Do not administer any fever-reducing medication, such as acetaminophen or ibuprofen, to a newborn before they have been examined by a healthcare provider. These medications can mask the fever, which is often the only symptom of a serious underlying infection, making diagnosis difficult. Before leaving for the emergency department, note the exact temperature, the time it was taken, and any other symptoms observed, such as feeding difficulties or changes in skin color.
There are other signs that warrant calling 911 immediately. These include difficulty breathing, new moaning or grunting noises with each breath, a bluish or gray tinge to the lips or face, or an inability to wake the baby. Being prepared with the details of your baby’s temperature and behavior allows the medical team to begin their assessment and testing process without delay.