Like the temperature of an adult, a baby’s temperature can fluctuate slightly based on things like time of day, activity, and even how the temperature was taken. In general, a child’s temperature should be between 97.7°F (36.5°C) and 99.5°F (37.5°C) when measured with an oral thermometer.

But taking an oral temperature in a baby isn’t accurate as they can’t hold the thermometer under their tongue. When taken with a rectal thermometer, a baby’s temperature should be about 99.6°F (37.6°C).

Taking a baby’s temperature under their arm (axillary) is another commonly used method that is easier, but still less accurate, than a rectal temperature. The axillary temperature is usually at least a degree lower than the rectal temperature.

If your baby’s temperature drops below 97.7°F (36.5°C), they’re considered to have hypothermia, or low body temperature. A low body temperature in babies can be dangerous, and, though rare, may lead to death.

Read on to learn more about low body temperature in babies, including causes and next steps.

In addition to a low body temperature, other symptoms of hypothermia in babies include:

  • sluggishness
  • poor feeding
  • weak cry
  • pale, cool skin
  • trouble breathing

1. Premature birth and low birth weight

Infants born at less than 28 weeks gestation have the highest risk of developing hypothermia. Low birth weight is another risk factor: Babies who are 3.3 pounds (1.5 kilograms) or less are 30 to 78 percent more likely to develop hypothermia immediately after birth than babies with a higher birth weight.

Early babies and those with low birth weight run a higher risk of hypothermia because of their large surface-area-to-volume ratio. Additional contributing factors are their:

  • lack of insulating body fat
  • immature nervous system
  • inability to efficiently conduct heat

Shortly after a hospital birth, if your baby is premature or has a low birth weight, they’ll be placed in specially designed bassinets that have warming lights and heated mattresses.

When you bring your baby home, use these tips to help regulate their body temperature:

  • Swaddle or wrap your baby snuggly in a single blanket.
  • Place a hat on your baby if they will be out in a cold environment. A hat may reduce heat loss by close to 19 percent in babies.
  • Limit baths. Water evaporating on skin can lower body temperature. Bathing, other than sponge bathing, isn’t recommended for babies until after the umbilical cord falls off.

2. Cold birth environment

Many babies, even full-term ones, are born with a near hypothermic body temperature. Being born in a cold space can quickly cause your baby’s body temperature to drop.

In the hospital, a number of protocols may be in place to warm up your baby, including:

  • immediately drying the baby after delivery to remove wet and cold amniotic fluid
  • placing the baby in a bassinet with radiant heat
  • using heated mattresses and blanket wraps
  • encouraging skin-on-skin contact with a parent
  • delaying the first bath until at least 12 hours after birth, when a baby may be a little more efficient at staying warm

If your baby is born outside of a hospital, it’s important to keep your baby warm using similar methods. While you may not have access to a heated mattress, you can dry your baby off, use skin-to-skin contact, and swaddle or wrap them in a blanket.

3. Hypoglycemia

Hypoglycemia is a condition in which there is too little glucose, or blood sugar, circulating in the body. Glucose is used by the body for energy. A baby can become hypoglycemic at birth or soon after because of infection, birth defects, or the mother’s health during pregnancy.

To help prevent hypoglycemia in your baby:

  • maintain a healthy diet during pregnancy and follow your doctor’s recommendations for weight gain
  • manage diabetes during pregnancy if you have that condition, and get tested for gestational diabetes
  • keep your baby on a regular feeding schedule

4. Infection

Some serious infections have been associated with a drop in body temperature.

Meningitis is an inflammation of the membranes that surround the spinal cord. It can sometimes cause a fever in babies, but in other cases it may cause a lower-than-normal body temperature.

Sepsis, a dangerous bacterial infection of the blood, commonly causes a low body temperature in infants, though in some cases it may lead to a fever instead.

Both meningitis and sepsis are serious, life-threatening infections. Get immediate medical help if you notice several of these symptoms in your baby:

  • pale, clammy, blotchy skin, and sometimes a rash
  • poor feeding
  • fast breathing
  • moaning cry
  • cold hands and feet

Low body temperature can be serious. When a baby’s temperature drops just one degree below 97.7°F (36.5°C), oxygen use increases 10 percent in an effort to generate more body warmth. That increase can put a huge stress on a tiny body.

In some cases, low body temperature may even lead to death, though this is exceedingly rare in the United States. In one study conducted in Nepal, researchers looked at newborns within the first 72 hours of birth and found that those with a body temperature of below 94.1°F (34.5°C) were 4.8 times more likely to die within a week of birth than those who had higher temperatures.

If you suspect your baby has a low body temperature, the first thing you should do is take their temperature. Rectal temperatures may be more accurate, but if you don’t have a rectal thermometer, you can use an axillary thermometer. Never use an axillary thermometer in the rectum or vice versa.

If your baby’s temperature is low and you’re unable to increase their temperature by adding clothing, using your body heat, or swaddling, call their pediatrician right away. You may be directed to seek emergency medical help. If you can’t reach them and your baby seems ill, go to the nearest emergency room.

Early treatment can help reduce the risk for serious complications. Always call your baby’s doctor if you suspect something is wrong. It’s better to err on the side of caution.

A body temperature lower than 97.7°F (36.5°C) puts a baby at increased risk for:

  • infections
  • respiratory problems
  • blood clotting disorders
  • death

Babies lose heat more rapidly than adults. If you notice any of the symptoms of hypothermia in babies — such as rapid or difficult breathing, pale skin, lethargy or a lack of interest in eating — try to increase your baby’s temperature with extra clothing and warm liquids, and seek medical help right away.

Be especially attentive if your baby was born early or at a low birth weight, as these children are more apt to experience a low body temperature than full-term babies.