Background The epidemiology of early-onset neonatal sepsis (EONS) varies over time, and requires regular surveillance.

Objective To analyse data on EONS in Australia and New Zealand.

Methods Retrospective analysis of data collected longitudinally from multiple neonatal units from 2002 to 2012.

Results Of 386 423 live births, 454 infants had EONS. The incidence rate of EONS was 1.20 per 1000 live births in 2002 and 0.83 in 2012, decreasing by 4% per year (95% CI 1% to 7%, p=0.007). Group B streptococcus (GBS) (37%) and Escherichia coli (25%) were the most prevalent organisms. The early-onset GBS (EOGBS) incidence rate was 0.43/1000 live births, with no evidence of change over time (p=0.3). Of EOGBS-infected babies, 62% were born at term compared with 8% with early-onset E. coli sepsis, p<0.0001. The mortality of E. coli early-onset sepsis (EOS) (25%) was higher than GBS (11%), but this difference in mortality was no longer significant after adjusting for gestation and birth weight. Mortality from EOS fell significantly over the study period (17% per year, 95% CI 10 to 24, p<0.0001).

Conclusions GBS was the most common cause of early sepsis, but the incidence was lower than prior to the introduction of intrapartum antibiotic prophylaxis, and remained steady over time. The mortality of early-onset E. coli sepsis was significantly higher than GBS sepsis, but this may have been because almost all babies with E. coli were born preterm, rather than a difference in virulence.