Objective: To determine the incidence of maternal bacteraemia during pregnancy and for 6 weeks postpartum, describe the gestation/stage at which sepsis occurs, the causative microorganisms, antibiotic resistance and review maternal, fetal and neonatal outcome., Design: Prospective review., Setting: Two tertiary referral, maternity hospitals in Dublin, Ireland., Population: During 2005-2012 inclusive, 150 043 pregnant women attended and 24.4% of infants born in Ireland were delivered at the hospitals., Methods: Demographic, clinical, microbiological and outcome data was collected from women with sepsis and compared with controls., Main Outcome Measures: Incidence, bacterial aetiology, gestation/stage at delivery, mode of delivery, antibiotic resistance, admission to augmented care, maternal, fetal and neonatal outcome., Results: The sepsis rate was 1.81 per 1000 pregnant women. Escherichia coli was the predominant pathogen, followed by Group B Streptococcus. Sepsis was more frequent among nulliparous women (odds ratio [OR] 1.39; 95% confidence interval [CI] 1.07-1.79) and multiple births (OR 2.04; 95% CI 0.98-4.08). Seventeen percent of sepsis episodes occurred antenatally, 36% intrapartum and 47% postpartum. The source of infection was the genital tract in 61% (95% CI 55.1-66.6) of patients and the urinary tract in 25% (95% CI 20.2-30.5). Sepsis was associated with preterm delivery (OR 2.81; 95% CI 1.99-3.96) and a high perinatal mortality rate (OR =5.78; 95% CI 2.89-11.21). Almost 14% of women required admission to augmented care. The most virulent organisms were Group A Streptococcus linked to postpartum sepsis at term and preterm Escherichia coli sepsis., Conclusions: Maternal sepsis is associated with preterm birth, a high perinatal mortality rate and nulliparous women., (© 2014 Royal College of Obstetricians and Gynaecologists.)