We emphasize again that the prevalence of maternal infections may vary in different populations, and others might arrive at different estimates about the percentage of infants colonized and, concerning those infants colonized, about the percentage with adverse outcomes. Additionally, many women are colonized or infected simultaneously with several of the organisms discussed in this review, and this may result in different projections of morbidity and mortality rates than those presented here. We realize also that new information is generated continually describing the relationship between various maternal colonizations and preterm birth, and that screening and treatment protocols for several diseases may reduce the prevalence of adverse outcomes reported here. Therefore, we emphasize that the prevalences of various adverse pregnancy outcomes, as presented in this article, are only approximations and may change as new information becomes available. Nevertheless, we believe it is reasonable to estimate the relative effect of various maternal sexually transmitted diseases on adverse pregnancy outcome as we have done in this article. By comparing the effect of direct transmission of sexually transmitted organisms on adverse outcomes with the effect on overall outcome through an increase in the rate of preterm births, we should be able to use this type of analysis to establish some basis for allocation of resources to future research as well as intervention programs aimed at reducing sexually transmitted disease-related adverse outcomes of pregnancy. Finally, the appreciation of the effect of bacterial vaginosis on outcomes of pregnancy associated with preterm birth gives bacterial vaginosis a greater public health importance than has been attributed to it in the past as the subject of sexually transmitted disease research and prevention.