An HIV positive woman can transmit the virus to her baby during pregnancy, labour and delivery, and through breastfeeding. If she takes no preventive drugs and breastfeeds then the chance of her baby becoming infected is around 20-45%.
Modern drugs are highly effective at preventing HIV transmission during pregnancy, labour and delivery. When combined with other interventions, including formula feeding, a complete course of treatment can cut the risk of transmission to below 2%. Even where resources are limited, a single dose of medicine given to mother and baby can cut the risk in half.