BACKGROUND Over 2 million children are thought to be living with HIV/AIDS worldwide, of whom over 80% live in sub-Saharan Africa. Without anti-retroviral treatment, the risk of HIV transmission from infected mothers to their children is 15-30% during gestation or labour, and 15-20% during breast feeding. HIV-1 infection accounts for most infections; HIV-2 is rarely transmitted from mother to child. Transmission is more likely in mothers with high viral loads and/or advanced disease, in the presence of other sexually transmitted diseases, and with increased exposure to maternal blood. METHODS We conducted a systematic review and aimed to answer the following clinical question: What are the effects of measures to reduce mother to child transmission of HIV? We searched: Medline, Embase, The Cochrane Library and other important databases up to January 2007 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). We performed a GRADE evaluation of the quality of evidence for interventions. RESULTS We found 18 systematic reviews, RCTs, or observational studies that met our inclusion criteria. CONCLUSIONS In this systematic review we present information relating to the effectiveness and safety of the following interventions: antiretroviral drugs, different methods of infant feeding, elective caesarean section, immunotherapy, vaginal microbicides, and vitamin supplements.