Vertical transmission is the dominant mode of acquisition of infection for HIV infection in children, and about 1600 infants are newly infected each day worldwide. Without interventions the risk of transmission is between 15% and 35%, and associated with maternal disease progression, prematurity, duration of rupture of membranes, length of labour, and vaginal delivery. Breastfeeding approximately doubles the risk of vertical transmission; the additional risk of transmission through breastfeeding is approximately 15-20%, with about one-third of this accounted for by late postnatal transmission after 3 months of age. Current strategies to reduce the risk of transmission include a short course of anti-retroviral therapy, avoidance of breastfeeding and Caesarean section delivery. However, even if interventions late in pregnancy or around the time of delivery are highly effective in preventing perinatal infection, it is likely that as a public health policy they are of interest only if alternatives to breastfeeding are feasible, affordable, safe and available.