Transmission routes

Transmission from mother to baby is known to occur in three ways:

• During pregnancy – the foetus is infected by HIV (in the mother's blood) crossing the placenta.
• During delivery – the infant is infected by HIV in the mother's cervical secretions or blood during childbirth.
• During breastfeeding – the infant is infected by HIV in the mother's breast milk or blood during breastfeeding.

The relative proportion of transmission occurring at these times is not yet clear, and may vary in different parts of the world.