Adults can keep their body temperature at a normal level because  they have a  tightly controlled thermostat.When you are cold, you shiver, helping to raise your body temperature. When you are overheated, you sweat to help you cool off. However this mechanism is not completely developed in newborns. Newborns lack the insulating fat layer that older babies and children have . As a result a newborn may not have a fever with an infection. Fevers in babies are usually caused by something more serious. You need to call your doctor right away if your baby is younger than 3 months old and has a rectal temperature of 100.4°F (38°C) or higher.

Infection

Fever is a normal response  to infection in adults. However only half of newborns with an infection have a fever. Some especially premature babies  have a lower body temperature with fever  and other signs such as change in behavior, feeding and color.

Overheating

It is important to keep a newborn from getting cold. However overheating  can occur with  many layers of clothing and blankets. Overheating can also occur at home, near heaters or near heat vents. It can also occur when a baby is over bundled in a heated car.

To avoid overheating , you have to do the following :

• Avoid placing a baby in direct sunlight , even through a window .
• Never leave a baby in a hot care for a minute. The temperature can rise quickly and cause heat stroke or death.

To prevent overheating, keep rooms at a normal temperature, about 72°F  to 75°F (22.2°C to 24° C), and dress your baby just like you and others in the room. An overheated baby may have a hot, red or flashed face and may be restless.

Low fluid intake and dehydration

Not taking in enough fluids can cause a baby’s body  temperature to rise. This may happen around the second or third day after birth. If fluids are not replaced by increased feedings, dehydration can occur and lead to serious complications. Intravenous IV fluids may be needed to  treat dehydration.