Temperature Percentiles by Hour of Life in the Newborn Nursery

To characterize temperature percentiles for infants at least 35 weeks' gestation through the first 48 hours of their birth hospitalization in the newborn nursery.

This retrospective cross-sectional study used electronic health record data from mothers and newborns admitted to a university-affiliated newborn nursery between May 2015 and August 2021. Axillary temperature values measured during the nursery stay were analyzed in prespecified time intervals to generate first, fifth, 50th, 95th, and 99th temperature percentiles from birth through 48 hours after birth. Descriptive, stratified subanalyses by infant sex, gestational age, birth weight, mode of delivery, and exposure to maternal peripartum fever were also conducted.

We analyzed 227 813 axillary temperature values from 23 352 infants. The median temperature ranged from 36.9 °C at birth to 37.0 °C at 48 hours following birth. The temperature range between the first and 99th percentile was widest at birth (36.1-38.4 °C, δ 2.3 °C) and narrowed thereafter to a range of 36.5 °C to 37.8 °C (δ 1.3 °C) at 48 hours following birth. Temperature percentiles did not differ by sex but did increase minimally with increases in gestational age and birth weight; however, 95% CIs often overlapped. Infants delivered via cesarean had lower temperatures at birth than infants born vaginally, and infants exposed to peripartum maternal fever had higher temperatures following birth than nonexposed infants.

These hour-specific temperature percentiles in late preterm and term infants in the newborn nursery strengthen the foundation for interpreting newborn temperatures in clinical context and highlight the need for more nuanced, evidence-based approaches to hypothermia evaluation and management.