How is HIV transmitted to a baby?

Transmission is the word for when HIV passes from one person to another.

Mother to baby transmission is known as vertical transmission.

This is a better term to use as it refers to the event rather than placing the onus and responsibility of transmission on the mother alone.

Most vertical transmissions happen near the time of or during labour and birth (when the baby is being born). Vertical transmission also includes transmission through breastfeeding.

The biggest risk factor for vertical transmission is the mother’s viral load. This is a measure of how much HIV is in your blood.

The main aim of ART is to get viral load to undetectable. This is the same for everyone with HIV. Viral load tests results are in copies per millilitre (copies/mL). Undetectable viral load is when this gets to less than 50 copies/mL.

When we talk about an undetectable viral load in this guide we mean less than 50. If a mother’s viral load is undetectable when her baby is born – particularly if this has been the case throughout pregnancy – the risk of vertical transmission is just about zero.

Undetectable viral load is particularly important at the time of birth. Most risk factors for transmission are removed by reducing the amount of HIV in the blood to undetectable.

Practically all risk factors point to one thing: looking after women’s health.