Providing warmth is an instinctual extension of love that all parents want to give to their baby. But despite best intentions, sometimes an infant's temperature drops below normal. A low temperature in a baby is most often due to a cold environment or not enough clothes or blankets. But it can be a sign of a serious illness, such as an infection, metabolic disease or problems within the brain. Newborns -- especially premature babies -- are at greatest risk of low body temperature due to low body fat and a high skin-to-weight ratio, which causes more rapid heat loss compared to adults. According to the World Health Organization, a body temperature of less than 97.7 F on a rectal thermometer is below normal for an infant and requires immediate medical attention.
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Dressing the baby too lightly, a cold room and being outside in chilly weather are the most common causes of a low temperature in an infant. Because they get colder more quickly than adults, babies typically need one more layer than what adults feel comfortable wearing. That can be long sleeves when you feel comfortable in short, or a medium-weight blanket wrapped around the baby in addition to seasonally appropriate clothing. If your baby feels a little cool but is active and feeling well, increasing the room temperature or adding a layer of clothing or a blanket might be all that is needed. If in doubt, however, check the baby's temperature with a thermometer.
Infection is a less common but potentially very serious cause of a low temperature in a baby. Bacterial infections of the lungs, blood, urinary system or the fluid surrounding the brain and spinal cord are particularly concerning. Babies born prematurely or to mothers without prenatal care are at increased risk for infections. While infection can cause a fever, an infant's immune system is still developing, and low body temperatures can also occur. An infection often causes other signs and symptoms, including a low activity or energy level, decreased feeding, increased sleeping and irritability. These symptoms alone should prompt immediate medical evaluation of a baby, but if they occur in conjunction with a low temperature, emergency care is needed.
Metabolic and Endocrine Diseases
Rarely, a low temperature in an infant is due to an inborn metabolic disease or an abnormality affecting one of the body organs that aid in body temperature regulation. The adrenal, thyroid and pituitary glands are endocrine organs that play a role in the complex system of regulating body temperature through their effects on metabolism. Impaired metabolism can impair the body's ability to generate heat. Reduced function in any of these organs -- whether due to disease or a condition a child is born with -- can cause low body temperature. Similarly, insufficient blood sugar or impaired utilization of sugars in the body organs and tissues commonly results in a low temperature as the body reacts to lack of available energy. This situation can occur due to diabetes or another disease.
Neurologic Injuries and Conditions
Body temperature regulation involves a complex system that begins with temperature-sensing receptors in the skin and certain body organs that communicate with an area deep in the brain called the hypothalamus. Multiple responses activate when the hypothalamus receives messages that body temperature is low. These responses collectively work to reduce heat loss and increase heat generation in an effort to increase body temperature.
Brain injuries and abnormalities can impair its temperature-regulating functions. For example, bleeding in a baby's brain, particularly around the time of delivery, can result in seizures and body temperature instability. Fortunately, this occurs rarely in full-term infants. However, the risk of a brain bleed is increased in premature babies and with difficult births requiring a vacuum or forceps to deliver the baby. Brain tumors that invade or press on the hypothalamus or pituitary gland can also affect temperature regulation and result in low temperatures. Traumatic brain injuries or diseases affecting areas of the brain involved in body temperature regulation can have the same effect.
Some drugs can cause low body temperatures through suppression of normal metabolic functioning. For example, babies born to mothers who use opiate drugs, such as heroin and narcotic pain relievers, late in their pregnancy can go through withdrawal after delivery. A low body temperature can be one of the signs of withdrawal as the baby's metabolism readjusts to functioning without the narcotic medication. Accidental ingestion of alcohol or antipsychotic medications can also cause an abnormally low temperature in an infant.
In addition, malnutrition can cause low temperature in an infant, as low body fat and muscle mass lead to a sluggish metabolism and reduced heat production. Sometimes malnutrition is due to child abuse or neglect. But it can also occur in babies who have challenges taking in the necessary minimum calories. Severe heart disease, significant facial malformations, digestive system problems, and malabsorption due to cystic fibrosis or inherited enzyme deficiencies can all make it difficult for babies to meet their daily caloric needs.
Warnings and Precautions
A borderline or low body temperature in a baby can be due to something as simple as needing another blanket, a light hat or a warmer onesie. However, it can also be a sign of a serious, potentially life-threatening disease. Signs and symptoms of low body temperature in a baby include: -- Cool or cold skin. -- Pale, blue, mottled or reddened skin. -- Reduced activity or energy. -- Weak cry. -- Poor feeding or unwillingness to feed. -- Breathing irregularly, or too rapidly or slowly.
A baby with a temperature less than 97.7 F or any signs or symptoms consistent with a low body temperature requires immediate medical evaluation.
Reviewed by: Tina M. St. John, M.D.