Incidence of Neonatal Hypothermia in the Newborn Nursery and Associated Factors

Abstract

ImportanceThermoregulation is a key component of well-newborn care. There is limited epidemiologic data on hypothermia in late preterm and term infants admitted to the nursery. Expanding on these data is essential for advancing evidence-based care in a population that represents more than 3.5 million births per year in the US.ObjectiveTo examine the incidence and factors associated with hypothermia in otherwise healthy infants admitted to the newborn nursery following delivery.Design, Setting, and ParticipantsA retrospective cohort study using electronic health record data from May 1, 2015, to August 31, 2021, was conducted at a newborn nursery at a university-affiliated children’s hospital. Participants included 23 549 infants admitted to the newborn nursery, from which 321 060 axillary and rectal temperature values were analyzed.ExposuresInfant and maternal clinical and demographic factors.Main Outcomes and MeasuresNeonatal hypothermia was defined according to the World Health Organization threshold of temperature less than 36.5 °C. Hypothermia was further classified by severity (mild: single episode, temperature 36.0-36.4 °C; moderate/severe: persistent or recurrent hypothermia and/or temperature <36.0 °C) and timing (early: all hypothermic episodes occurred within the first 24 hours after birth; late: any episode extended beyond the first 24 hours).ResultsOf 23 549 included infants (male, 12 220 [51.9%]), 5.6% were late preterm (35-36 weeks’ gestation) and 4.3% were low birth weight (≤2500 g). The incidence of mild hypothermia was 17.1% and the incidence of moderate/severe hypothermia was 4.6%. Late hypothermia occurred in 1.8% of infants. Lower birth weight and gestational age and Black and Asian maternal race and ethnicity had the highest adjusted odds across all classifications of hypothermia. The adjusted odds ratios of moderate/severe hypothermia were 5.97 (95% CI 4.45-8.00) in infants with a birth weight less than or equal to 2500 vs 3001 to 3500 g, 3.17 (95% CI 2.24-4.49) in 35 week’ vs 39 weeks’ gestation, and 2.65 (95% CI 1.78-3.96) in infants born to Black mothers and 1.94 (95% CI 1.61-2.34) in infants born to Asian mothers vs non-Hispanic White mothers.Conclusions and RelevanceIn this cohort study of infants in the inpatient nursery, hypothermia was common, and the incidence varied by hypothermia definition applied. Infants of lower gestational age and birth weight and those born to Black and Asian mothers carried the highest odds of hypothermia. These findings suggest that identifying biological, structural, and social determinants of hypothermia is essential for advancing evidence-based equitable thermoregulatory care.

Management and Clinical Outcomes of Neonatal Hypothermia in the Newborn Nursery

“…Our prior manuscript on the epidemiology of hypothermia in the nursery found that both birth weight (BW) and GA were associated with hypothermia. 4 Therefore, in the current study, we performed a sensitivity analysis adding BW as a confounder to all models that adjusted for GA.…”

“…2 "Moderate/Severe" hypothermia was defined as having an episode lasting ≥2 hours, at least episodes of hypothermia, and/or hypothermia <36.0˚C or lasting >2 hours 3 Column percentages may not add up to 100% due to rounding 4 Small-for-gestational age is defined as below the 10 th percentile using the Olsen intrauterine growth curves 48 5 Race, Ethnicity, and Language data are self-reported fields. "Unknown" is the default option and includes patients that decline to answer the question.…”

“…Neonatal hypothermia is common in the newborn nursery. [1][2][3][4] In our prior study of >23,000 infants admitted to the nursery, we demonstrated that 21.7% infants had at least one episode of hypothermia, 4 defined using the World Health Organization (WHO) threshold of <36.5˚C. 5 In high-risk preterm (≤33 weeks' gestation) and/or very low birth weight (<1,500 g) infants admitted the Neonatal Intensive Care Unit (NICU), hypothermia has been associated with mortality and morbidity, including sepsis, intraventricular hemorrhage, bronchopulmonary dysplasia, necrotizing enterocolitis, and retinopathy of prematurity.…”