Current strategies to prevent infection-related preterm birth and its associated neonatal morbidities have had limited success. Improved understanding of the pathogen-host interactions underlying altered colonization of the lower genital tract is necessary before significant progress can be made. The application of novel diagnostic techniques such as broad range PCR and proteomic analysis contribute to our knowledge of the diversity and abundance of microbial species invading the amniotic cavity as well as the resultant inflammatory response. Preterm infants delivered following intrauterine infection may respond differently to subsequent infectious challenges in the neonatal intensive care unit.