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Assessing Fever in the Newborn


Article By:

M. Ansari

U. Pandya



Fever in a new born is a medical emergency, since a well looking neonate may be carrying a serious infection, which may delay diagnosis. It is a sign of probable serious bacterial infection. While taking a neonate’s temperature, it is important to know the difference between the normal body temperatures of that of an adult and a newborn. The normal body temperature in a neonate is higher as compared to adults and varies between 36.5o to 37.5o centigrade (C) axillary temperature and exhibits a normal circadian diurnal variation, that is, being lowest between midnight to 6 am and maximum between 5 pm to 7 pm.



A neonate with a body temperature higher than 37.5oC is considered as abnormally warm. Blood vessels of the neonate will be dilated, and hands and feet are warm to touch. The baby acquires spread eagle posture after hyperthermia.[1] Both mercury and electronic thermometers are available. While digital thermometers have calibration errors, they are preferred over mercury thermometers because of the latter’s risk of breaking leading to poisoning in infants.[2]


Mechanisms causing fever:

Mechanisms are probably from an imbalance between heat production and heat displacement however, these are still poorly understood. Newborns can have severe bacterial infections without increased body temperature. Newborn infants have poor heat loss mechanisms (absence of sweating); therefore, either an exposure to excess  heat  or  excess  insulation  (e.g., excessive swaddling) or combination of both can quickly increase their core temperature. Such overheating commonly occurs when term babies are nursed in uncontrolled incubators or under radiant warmers. Fever in low birth weight and premature infants is more common due to uncontrolled incubators.[3]


Causes of neonatal hyperthermia:

It is important to remember that sepsis is not a common cause of fever. Neonates with sepsis more frequently have hypothermia. However, infection is probably the most treatable life-threatening cause occurring in infants with fever. Infections within 48 hours of birth are likely from maternal transmission.  Most  likely organisms are Group B streptococcus, S.pneumoniae and Escherichia Coli. After that it is more likely to have nosocomial infections.

Dehydration is other common cause of fever in the newborn period. Due to inadequate milk intake, dehydration fever occurs most commonly in healthy full term newborns. It occurs most commonly on 3rd to 4th day of life.  Dehydration fever is commonly seen in large full term breastfed newborns whose milk intake is inadequate; Newborns exposed to high environmental temperatures during the summertime may have dehydration fever. Rehydration leads to resolution of fever of dehydration fever.

Hyperthermia has been reported in premature infants as a complication of improper use of convection-warmed incubator or radiant warmer conditions. Babies should always have strictly monitored and servo-controlled source of heat.

Unexplained neonatal fevers were associated with the introduction of routine hepatitis B vaccination in routine immunization schedules. But it was not confirmed in subsequent large multicentre trials. Uncommon causes include congenital malaria, typhoid fever, intracranial haemorrhages, and myelopathy.


Signs and symptoms:

A newborn with a temperature that is even slightly above the normal range should be taken to the doctor as soon as possible; further, if the newborn has any of the following symptoms, he or she must be brought to a hospital for thorough evaluation.

  • Excessive and continuous crying
  • Irritability
  • Listless baby
  • Convulsions
  • Excessive weight loss
  • Decreased urine output
  • Difficulty in breathing
  • Refusing to breastfeed
  • Trouble swallowing
  • Vomiting or diarrhoea



Since fever is only a symptom, treatment of the underlying cause is important. Investigations and thorough physical examination must be done to rule out every possible cause of hyperthermia. Given below is an algorithm for assessing an infant under 90 days age (Table 1).

TC-Oct 2018-012 - Table 1 Evaluation of fever in an infant less than 3 months old

A febrile neonate requires a detailed assessment. A neonate with a toxic appearance has high risk of serious bacterial infections and should be treated aggressively. In this situation, hospital admission is warranted to undergo a complete sepsis evaluation. Full course of antibiotics with adequate fluid management must be done. 

An infant’s environment should be examined for overheating. In exclusively breastfed infants, fever at 3 to 4 days of age with excessive weight loss, dehydration fever should be considered and treated appropriately after establishing the diagnosis. Proper latching on techniques ensuring adequate breast feeding is the key in treatment of neonatal hyperthermia.

The antipyretic drug used commonly in neonates is paracetamol. Considering all factors, it is reasonable to use paracetamol at dose of 15 milligram per kilogram body weight (mg/kg) every 4 hourly (max 5-6 doses/day). Tepid water sponging may be used as a complimentary method to drug therapy in bringing down the fever quickly.

Therapy with antibiotics (third generation cephalosporines e.g. cefotaxime, ceftriaxone, with or without aminoglycosides) should be initiated while awaiting the results of investigations. Supportive therapy should be instituted, as required.[2]

TC-Oct 2018-013 - Authors Pg20


  1. Martin R, Fanaroff A, Walsh M. Fanaroff and Martin’s neonatal-perinatal medicine. St. Louis, Mo.: Elsevier; 2011.
  2. Paul, VK, Bagga A. GhaiEssential Pediatrics, New Delhi, Delhi. CBS Publishers and Distributors Pvt Ltd. 2013.
  3. Gleason C, Devaskar S, Avery M. Avery’s diseases of the newborn. Elsevier; 2012.