Background and aims The perinatal factors associated with hypothermia at admission and it relation with morbidity and mortality during the neonatal period has not been systematically studied in our area. We aimed to know the temperature on admission of infants ≤26 weeks GA and to determine whether it was associated with perinatal variables and with selected morbidities and mortality.

Methods We included inborn infants ≤26 weeks GA without major congenital anomalies, admitted to the NICUs participating in the Spanish SEN1500 network, during the period 2006–2010. We used multivariable linear or logistic regressions to detect independent associations.

Results 1,749 inborn infants were included. The mean admission temperature was 35.5 ± 0.9ºC (range: 33.1–39.0ºC). The proportion of infants with a temperature <36.5ºC was 85.8%. The association between perinatal variables with admission temperature was:

Conclusions Hypothermia on admission is frequent among infants ≤26 weeks GA, and is associated with lack of antenatal steroid, lower birth weight, vaginal delivery, multiplicity and neonatal depression. A low temperature on admission is related to an increased risk of BPD, IVH and mortality. After adjusting for potential confounders, temperature on admission was related with a reduction in BPD (OR 0.797; 95% CI 0.666–0.954; p = 0.013), severe HIV (OR 0.844; 95% CI 0.734–0.970; p = 0.017), and an increase in survival (OR 1.384; 95% CI 1.213–1.580; p < 0.001).