This is an overview of evidence of the effectiveness of antenatal care in relation to maternal mortality and serious morbidity, focused in particular on developing countries. It concentrates on the major causes of maternal mortality, and traces their antecedent morbidities and risk factors in pregnancy. It also includes interventions aimed at preventing, detecting or treating any stage along this pathway during pregnancy. This is an updated and expanded version of a review first published by the World Health Organization (WHO) in 1992. The scientific evidence from randomised controlled trials and other types of intervention or observational study on the effectiveness of these interventions is reviewed critically. The sources and quality of available data, and possible biases in their collection or interpretation are considered. As in other areas of maternal health, good-quality evidence is scarce and, just as in many aspects of health care generally, there are interventions in current practice that have not been subjected to rigorous evaluation. A table of antenatal interventions of proven effectiveness in conditions that can lead to maternal mortality or serious morbidity is presented. Interventions for which there is some promising evidence, short of proof, of effectiveness are explored, and the outstanding questions formulated. These are presented in a series of tables with suggestions about the types of study needed to answer them.