Premature delivery is still a significant problem in Obstetrics. It has multiple causes, with around 50% thought due to infection. Of note infection as a pathogenesis is more likely in those pre-term births occurring <30 weeks gestation and is largely sub-clinical. Potential pathogens largely arise from the ascending route and from the endogenous vaginal flora, causing chorioamnionitis. Resultant morbidity from the release of endo+/exotoxins from such pathogens, the stimulation and production of inflammatory cytokine pathways, prostaglandins, metalloproteinases includes maternal sepsis (chorioamnionitis, septicaemia, post-partum endometritis), pre-term delivery (infant pre-maturity and its consequences, increased susceptibility to cerebral palsy and neonatal sepsis). As well, infection increases mortality due to fetal loss (extreme pre-maturity) as well as severe neonatal sepsis.