Objective To assess the seasonal pattern of healthcare-associated infections (HCAI) among neonates and to describe the trend of HCAI.

Design Secondary analyses of database.

Setting The Canadian Neonatal Network database (2003–2009).

Participants Neonates with HCAI defined as blood/cerebrospinal fluid positive with pathogenic organism in a symptomatic infant after 2 days of age.

Main outcome measure The incidence rate for HCAI per 1000 days with a 95% CI, for the 4 warmest months (June–September) was compared with the remaining 8 months, to calculate the incidence rate ratio (IRR).

Results Of 75 629 total infants, 4305 (5.7%) had HCAI (3367 had 1 and 938 had >1 episodes). Infants who had HCAI were of lower gestation, birth weight and Apgar score; but had higher severity of illness scores and clinical chorioamnionitis. There was a borderline increase in all HCAI (IRR 1.05, 95% CI 1.00 to 1.11) and a significant increase in Gram-negative HCAI (IRR 1.20, 95% CI 1.04 to 1.39) during the summer months. Overall, there was a 20% reduction in HCAI from 4.45/1000 days in January 2003 to 3.54/1000 days in December 2009 (mean difference 0.91/1000 days (95% CI 0.89 to 0.92).

Conclusions Gram-negative infections were significantly increased during the summer months of the year compared with the rest of the year among neonates. Overall, there was a significant temporal reduction in HCAI rates over the study period.