Hypothermia is well recognized as a factor influencing newborn health.1–8 Despite this recognition, hypothermia remains a significant challenge, especially in the perinatal care of preterm infants. Our clinical experience suggests that hypothermia remains an ongoing problem, especially among extremely low birth weight infants, even for those born in Level III perinatal centers. Preterm delivery less than 28 weeks or less than 1000 g occurs in 1-2% of all deliveries, but accounts for the large majority of neonatal morbidity and mortality. Therefore, the possibility that perinatal hypothermia is a contributing factor to adverse outcomes among this population deserves special attention.
The newborn infant exhibits immature thermoregulation, as compared with the older child or adult and therefore needs to be protected from extremes of cold and heat. In 1997, the World Health Organization (WHO)1 provided the following definitions of normothermia and hypothermia:
- Normal range: 36.5-37.5 °C
- Potential cold stress: 36.0-36.5°; cause for concern
- Moderate hypothermia: 32.0-36.0°; danger, immediate warming of the baby needed
- Severe hypothermia: less than 32.0°; outlook grave; skilled care urgently needed.
There are a number of potential causes for hypothermia in the newborn infant, which are summarized in Table 1.
All of these sources of hypothermia can be problems in delivery room resuscitation efforts, as well as during transport of the preterm infant to the neonatal intensive care unit and during certain neonatal intensive care unit admitting procedures such as weighing the baby.
There is general agreement that perinatal hypothermia should be avoided in all newborns, with the possible exception of those who have sustained a significant hypoxic-ischemic insult. In 2006, the American Academy of Pediatrics' and American Heart Association's Neonatal Resuscitation Program (NRP) textbook2 recommended, ‘the goal (of the first postnatal temperature) should be an axillary temperature of approximately 36.5 °C’. The NRP text also noted that ‘temperature must be monitored closely because of the slight but described risk of hyperthermia... (which) during or after ischemia is associated with progression of cerebral injury... The goal is to achieve normothermia and avoid iatrogenic hyperthermia’. Continuous temperature monitoring should be initiated as soon as possible after the birth of the preterm infants in order to document and achieve normothermia. Since low delivery room temperatures can predispose to hypothermia,3 the NRP text recommended, ‘when delivery of a preterm baby is anticipated, the temperature of the room should be increased’, and to ‘pre-heat the radiant warmer by turning it on well before birth, use a head cap, and ... if the baby is born at less than 28 weeks gestation, consider placing him, below the neck, in a reclosable polyethylene bag, without first drying the skin. The bag can be a standard 1-gallon, food-quality, polyethylene bag purchased in a grocery store.’
Another way to improve temperature regulation in the delivery room is to actively share American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE)9 and WHO1 recommendations for delivery room temperatures with hospital leaders and managers of Labor and Delivery services. The ASHRAE handbook recommends single room labor-delivery-recovery-postpartum temperature of 75 ± 2 °F, standard patient room temperature of 75 ± 2 °F, recovery room temperature of 75 ± 2 °F and nursery temperature of 75 ± 3 °F. The guidelines further state that Delivery Room temperature should never be below 68 °F. Recommendations from the American Institute of Architects (AIA),10 WHO and Recommended Standards for Newborn ICU Design11 are in agreement with the ASHRAE document. Prevention of hypothermia is also enhanced by use of weighing scales built into warmers and appropriate attention to adequate warming mechanisms of transport incubators. However, of paramount importance is staff education in this area on the problem of neonatal hypothermia and the use of preventive strategies, especially in the extremely low birth weight infant.
Current data: prevalence of hypothermia among low birth weight infants
A number of American Academy of Pediatrics colleagues recently shared the following quality improvement data regarding hypothermia (defined as a temperature ≤ 36.4 °C or ≤ 97.6 °F) at admission to their units from the delivery room within 30 min of birth (Table 2).
These data show a continuing high prevalence of hypothermia among low birth weight preterm infants, with all centers reporting an incidence of at least 25% among infants < 2500 g birth weight, and 56% or greater in infants <750g.
Hypothermia is a potentially preventable event in nearly all infants, even those who are extremely low birth weight, and deserves special attention because of its association with substantial morbidity and mortality. Although multicenter clinical trials will be needed to establish best practices for prevention of hypothermia, the recommendations that follow have an extensive foundation in current experience and should be utilized until further data are available.
The delivery room temperature should be at or higher than that recommended for the labor-delivery-recovery-postpartum, patient room, recovery room and nursery, especially for the preterm infant (Table 3). In order to achieve and document this recommendation, every delivery room should have individual thermostat and humidity control, so that Labor and Delivery personnel can adjust the thermostat as needed for preterm deliveries. Delivery room temperatures and humidity at the time of each delivery should be documented, and each infant's temperature should be recorded as soon as possible after birth and every 10-15 min thereafter until continuous temperature monitoring has been established. It is important that monitoring consider the possibility of extremes in body temperature in either direction that can occur among extremely preterm infants. Over-warming resulting in hyperthermia of the newborn can occur and is equally dangerous.1,12
These arbitrary set points for delivery rooms are consensus-based and not evidence-based. One aspect, however, is clear: as recommended by the WHO, ‘adults should not determine the delivery room temperature according to their own comfort’.1 Discussions with members of the obstetrical team will be necessary to effect this change in the delivery room, especially during operative deliveries when gowning is used. It should be remembered that warming the delivery room above 72°F will be necessary in <2% of deliveries. Another potential approach is to have a dedicated room for newborn resuscitation adjacent to the delivery room in which ambient temperature can be well controlled.11
Neonatal hypothermia continues to be a significant concern, especially among extremely preterm infants. Preliminary information from our nonrandom sample of hospitals suggests that hypothermia among preterm newborns born at or below 1500 g varies from 31 to 78%. Although clinical trials data currently are lacking, it is likely that a number of measures will prove to reduce or prevent perinatal hypothermia among preterm infants. Currently, we recommend approaching this problem by following the NRP and ASHRAE recommendations for delivery room temperature management and also by joining efforts to study the most effective ways of enhancing thermoregulation in the very preterm infant. The goal of such interventions is to achieve normothermia and avoid iatrogenic hyperthermia.
The AAP Committee On Fetus and Newborn, Section on Perinatal Pediatrics, NRP, the California Association of Neonatologists and District IX of the AAP Section on Perinatal Pediatrics are working together to assess the magnitude of this problem and support institution of measures to prevent hypothermia among preterm neonates.
2. Kattwinkel J (ed). Textbook of Neonatal Resuscitation. 5th edn, American Academy of Pediatrics: Elk Grove Village, IL, 2006, Lesson 8 6.
3. Knobel RB, Wimmer JE, Holbert D. Heat loss prevention for preterm infants in the delivery room. J Perinatol 2005; 25: 304–308.
4. Knobel RB, Vohra S, Lehmann CU. Heat loss prevention in the delivery room for preterm infants: a national survey of newborn intensive care units. Perinatol 2005; 25: 514–518.
5. McCall EM, Alderdice FA, Halliday HL, Jenkins JG, Vohra S. Interventions to prevent hypothermia at birth in preterm and/or low birthweight babies. Cochrane Database of Systematic Reviews 2005; (Issue 1). Art. No.: CD004210.
6. Watkinson M. Temperature control of premature infants in the delivery room. Clin Perinatol 2006; 33: 43–53
7. Costeloe K, Hennessy E, Gibson A, Marlow N, Wilkinson AR. The EPICure study: outcomes to discharge from hospital for infants born at the threshold of viability. Pediatrics 2000; 106: 659–671.
8. Vohra S, Roberts RS, Zhang B, Janes M, Schmidt B. Heat Loss Prevention (HeLP) in the delivery room: a randomized controlled trial of polyethylene occlusive skin wrapping in very preterm infants. J Pediatr 2004; 145: 750–753.
9. 2003 Handbook: HVAC Applications. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE): Atlanta, GA, 2003.
10. Guidelines for Design and Construction of Health Care Facilities. American Institute of Architects (AIA): Washington, DC, 2006.
11. White RD, Smith J, Philbin MK, Graven S, Martin G, Kolberg K et al
. Recommended Standards for Newborn ICU Design. Perinatol. 7th edn, 2007. this supplement.
12. Newton T, Watkinson M. Preventing hypothermia at birth in preterm babies: at a cost of overheating some? Arch Dis Child Fetal Neonatal Ed 2003; 88: F256.