Normal range and risk factors for deviating body temperatures during the first 24 hours in term-born infants under standardised care: an observational study.

OBJECTIVE: Body temperature for a known ambient temperature is not known for infants born at term. We aimed to determine the normal range and the incidences of hypothermia and hyperthermia during the first 24 hours of life in healthy term-born infants nursed according to WHO recommendations. DESIGN: Prospective observational study. SETTING: Norwegian single centre district hospital. Infants were observed during skin-to-skin care or when dressed in cots. PARTICIPANTS: Convenience sample of 951 healthy infants born at term. METHODS: Delivery room temperature was aimed at 26-30°C and rooming-in temperature at 24°C. We measured rectal and room temperatures at 2, 4, 8, 16 and 24 hours of age. MAIN OUTCOME MEASURES: Percentile curves for rectal temperature. Proportions and risk factors for hypothermia and hyperthermia. RESULTS: The mean (SD) room temperature was 24.0°C (1.1), 23.8°C (1.0), 23.8°C (1.0)., 23.7°C (0.9) and 23.8°C (0.9). The median (2.5, 97.5 percentile) rectal temperature was 36.9°C (35.7-37.9), 36.8°C (35.9-37.5), 36.9°C (36.1-37.5), 37.0°C (36.4-37.7) and 37.1°C (36.5-37.7). Hypothermia (<36.5°C) occurred in 28% of the infants, 82% of incidents during the first 8 hours. Risk factors for hypothermia were low birth weight (OR 3.1 (95% CI, 2.0 to 4.6), per kg), male sex, being born at night and nursed in a cot versus skin to skin. Hyperthermia (>37.5°C) occurred in 12% and most commonly in large infants after 8 hours of life. Risk factors for hyperthermia were high birth weight (OR 2.2 (95% CI, 1.4 to 3.5), per kg), being awake, nursed skin to skin and being born through heavily stained amniotic fluid. CONCLUSIONS: Term-born infants were at risk of hypothermia during the first hours after birth even when nursed in an assumed adequate thermal environment and at risk of hyperthermia after 8 hours of age.

Heart rate during the first 24 hours in term-born infants.

OBJECTIVE: Heart rate (HR) is an important clinical parameter in newborn infants, but normal ranges are poorly defined. Our aim was to establish normal reference ranges and individual variations in HR as obtained by auscultation in healthy term-born infants during the first 24 hours of life. DESIGN: Observational study. SETTING: Single hospital in Norway. METHODS: HR was assessed by auscultation for 30 s at 2, 4, 8, 16 and 24 hours of age. Auscultation was validated against ECG recordings. SUBJECTS: Healthy term-born infants who were asleep or awake in a quiet resting state. MAIN OUTCOME MEASURES: Construction of percentile curves for resting HR. RESULTS: The study included 953 infants. The 50th percentile was 126 beats per minute (bpm) at age 2 hours and thereafter 120-122 bpm. The respective 2nd and 98th percentiles were 102 (thereafter 96-100) bpm and 162 (thereafter 150-156) bpm. The mean HR was 5.6 bpm higher when awake than asleep, 4.9 bpm higher when on the mother's chest than in the cot, 1.6 bpm higher in girls than in boys, and increased by 0.5 bpm per 0.1°C increase in rectal temperature. Mode of delivery, meconium staining, birth weight and maternal smoking during pregnancy were of no significance. For each infant, HR varied considerably during the first 24 hours (intraclass correlation 0.21 (95% CI 0.18 to 0.24), coefficient of variation 9.2%). CONCLUSIONS: The HR percentiles allow for a scientifically based use of HR when assessing newborn infants born at term.

Respiratory Rate During the First 24 Hours of Life in Healthy Term Infants.

BACKGROUND AND OBJECTIVE: Abnormal respiratory rate (RR) is a key symptom of disease in the newborn. The aim of this study was to establish the reference range for RR during the first 24 hours of life in healthy infants born at term. METHODS: Infants were included at the hospital postnatal ward when time permitted. During sleep or a defined quiet state, RR was counted at 2, 4, 8, 16, and 24 hours by placing the bell of a stethoscope in front of the nostrils and mouth for 60 seconds. Data on maternal health, pregnancies, and births were obtained from medical records and the Medical Birth Registry of Norway. RESULTS: The study included 953 infants. Median RRs were 46 breaths/minute at 2 hours, thereafter 42 to 44 breaths/minute. The 95th percentile was 65 breaths/minute at 2 hours, thereafter 58 to 60 breaths/minute. The fifth percentile was 30 to 32 breaths/minute. Within these limits, the intraindividual variation was wide. The overall mean RR was 5.2 (95% confidence interval [CI], 4.7 to 5.7, P < .001) breaths/minute higher while awake than during sleep, 3.1 (95% CI, 1.5 to 4.8, P < .001) breaths/minute higher after heavy meconium staining of the amniotic fluid, and 1.6 (95% CI, 0.8 to 2.4, P < .001) breaths/minute higher in boys than girls. RR did not differ for infants born after vaginal versus cesarean deliveries. CONCLUSIONS: The RR percentiles established from this study allow for a scientifically based use of RR when assessing newborn infants born at term.