Fevers in Newborns
Fevers in Newborns
Everyone’s body has an “internal thermostat” used to regulate body temperature. Older children and adults shiver when cold to help raise body temperature and sweat when overheated to lower it. In newborns, however, these mechanisms used to regulate body temperature are not fully developed. Newborns also do not yet have the insulating layer of fat that older babies and children acquire. Because of their inability to regulate their body temperature effectively, newborns may not get a fever at all when sick with an infection or may even have a low body temperature. However, infants younger than 3 months old with a rectal temperature of 100.4℉ (38℃) and higher could indicate a dangerous infection and is considered an emergency. These infants require immediate medical attention even if they appear well and show no other signs of illness.
What Causes a Fever in Newborns?
According to the American Academy of Pediatrics (AAP), approximately 14 out of every 1,000 healthy infants born full-term develop a fever between 8 and 60 days old. While most of these fevers do not progress to serious illness, it can be difficult to determine the cause of the fever in an infant quickly while also avoiding any unnecessary tests or hospitalizations. The AAP also finds that more than 10% of young infants with a fever are diagnosed with a urinary tract infection (UTI), therefore it is important to have a urine sample checked. While less common, more serious, rapidly-progressing bacterial and viral infections may cause a fever such as meningitis, pneumonia, sepsis, and gastroenteritis.
What Should I Do if My Newborn Has a Fever?
Infants younger than 2 months old—Go to the emergency department immediately if your child younger than 2 months old has a rectal temperature of 100.4℉ (38℃) or higher.
Infants between 2 and 3 months old—Call your child’s primary care provider immediately if your child between 2 and 3 months old has a temperature of 100.4℉ (38℃) or higher (taken any way).
Infants older than 3 months—Call your child’s primary care provider right away if your infant has a fever and:
Looks or acts very sick
Is crying inconsolably
Is difficult to awaken
Has been in a very hot place (like inside of a car)
Other symptoms like severe headache, stiff neck, severe throat or ear pain, repeated vomiting or diarrhea, or an unexplained rash
Has signs of dehydration like a sunken soft spot, less wet diapers/peeing less than usual, no tears when crying, or dry mouth
Is taking steroids or has other immune system problems such as cancer
Has had a seizure
Has a fever above 104℉ (40℃) repeatedly
Still acts sick after the fever comes down or seems to be getting worse
Has a fever for more than 24 hours
Other Causes of Increased Body Temperature in Newborns and Infants
Heatstroke vs. Fever—What’s the Difference?
Fever should not be confused with heatstroke or other heat-related illnesses. A fever is caused by an infection, whereas heatstroke and heat-related illnesses are caused by environmental heat overheating the body to dangerous temperatures above 105℉ (40.5℃). This can happen when a newborn is overdressed or wrapped in a blanket as they are unable to regulate their body temperature as well as older children. It can also happen if a child is left unattended in overheated cars. Never leave your baby or child unattended in a closed car, even if just for a few minutes. Call 911 or go to the emergency department right away if you think your child has heatstroke.
Low Fluid Intake or Dehydration
Some infants may not get enough breastmilk or formula, and dehydration (or excessive loss of body water) may develop. This can cause an increase in body temperature and could result in serious complications. It is important to contact your child’s primary care provider (PCP) right away if you suspect your infant is dehydrated or is not eating enough breastmilk or formula. Intravenous (IV) fluids may be needed to treat dehydration.
Key Points to Remember
While a fever in older babies and children are signs that the immune system is working properly and may require no treatment at all, a fever in a newborn or infant less than 3 months old is considered a medical emergency requiring immediate medical attention. It is important to quickly rule out possible dangerous infections in these newborns and infants in a hospital setting. Infections cause fevers, but there are other conditions that can raise a baby’s body temperature as well such as dehydration, heatstroke, or other heat-related illnesses—all of which require immediate medical attention.
For More Information on Fevers in Children:
