Keeping Baby Warm: Thermoregulation in the Neonate
Published: 25 September 2023
Published: 25 September 2023
Creating a thermoneutral environment is essential for the wellbeing of newborn babies, especially for those who are born prematurely or who need special or intensive care.
So, what is a thermoneutral environment, and how can it be created and maintained?
Thermoregulation is the ability to balance heat production and heat loss to maintain steady, normal body temperature, with a stable metabolic state where minimal rates of oxygen consumption or energy expenditure occur (RCHM 2020).
To put it more simply, a neutral thermal environment is the optimum environmental temperature to ensure an infant has the lowest oxygen and energy expenditure whilst maintaining a normal body temperature. Each infant has their own neutral thermal environment depending on their birth weight, gestation and whether or not they are clothed (North Devon Healthcare NHS Trust 2018).
An ideal thermoneutral environment is achieved when infants can maintain their core body temperature at rest between 36.5 ℃ and 37.5 ℃ (RCHM 2020). Too much heat, or too little, can result in thermal stress in the form of hyperthermia, or more commonly, hypothermia or excessive heat loss (CHW 2021).
Without the ability to maintain a steady body temperature, cold stress and hypothermia can occur, leading to serious metabolic problems and the potential risk of morbidity or mortality (CHW 2021)
Some of the reasons why babies are prone to poor thermoregulation at birth include:
(Morrin et al. 2017)
Axillary temperature measurement is usually recommended for full-term newborn infants (North Devon Healthcare NHS Trust 2018).
The standard range of body temperatures for a healthy term newborn is:
< 32.0 ºC | Severe hypothermia |
32.0 - 35.9 ºC | Moderate hypothermia |
36.0 - 36.4 ºC | Mild hypothermia |
36.5 - 37.5 ºC | Normal range |
> 37.5 ºC | Hyperthermia |
(Adapted from SLHD 2022)
Hypothermia or cold stress is known to occur via four principal methods:
(Morrin et al. 2017)
It’s well known that hypothermia has a direct relationship with increased mortality and morbidity, with a 28% increase in mortality for each 1 ºC drop in temperature. Rapid heat loss of up to 1ºC per minute can occur in infants nursed in an inappropriate environment, highlighting the importance of accurate temperature measurement (Morrin et al. 2017).
In particular, excessive heat loss can lead to acidosis due to the metabolism of fatty acids, as well as increased oxygen consumption leading to episodes of hypoxia. Other complications caused by hypothermia include increased glucose uptake, which may result in hypoglycaemia as well as postnatal weight loss or failure to gain weight (Morrin et al. 2017).
An ideal thermoneutral environment is achieved when infants can maintain a core temperature at rest of between 36.5 ºC and 37.5 ºC, but for certain infants, this may require extra monitoring and interventions. Those most at risk include infants:
(Morrin et al. 2017)
Brown adipose tissue is mainly found in nuchal subcutaneous tissue around the kidneys, the mediastinum and interscapular regions (RCHM 2020).
When their temperature falls below 36.5 °C, newborn infants peripherally vasoconstrict and initiate a non-shivering thermogenesis of brown adipose tissue (RCHM 2020). However, as brown fat only starts to form from 26 weeks gestation and development stops post-delivery, it can leave many preterm babies at greater risk of cold stress. With continued hypothermia, stores of brown fat can become depleted, resulting in hypoxia and hypoglycaemia (Waldron & MacKinnon 2007).
Premature infants and those suffering intrauterine growth restriction are particularly at risk of hypothermia as they have less brown fat stores, decreased fat for insulation, decreased glycogen stores, immature skin that increases water loss, poor vascular control, a slower metabolism and a narrower range of thermal control (RCHM 2020).
Some of the signs that a preterm infant is having difficulty keeping warm include:
(North Devon Healthcare NHS Trust 2018)
Temperature monitoring in the newborn is a well-researched and standard procedure for all infants in the first few days of life. For premature babies or those born with growth restriction, it becomes even more important as the risk of hypothermia and cold stress is increased.
Yet, with care and interventions to prevent heat loss, such as skin-to-skin contact, coverings such as wraps and hats, or incubator care for those who need it, the thermoneutral environment can easily be maintained.