How likely is mother-to-child transmission?

In the absence of any intervention, an HIV-positive woman has a 30 to 45% chance of transmitting the virus to her baby.

• Approximately 5 to 10% of infants are infected during pregnancy.
• Approximately 10 to 20% are infected during childbirth.
• Approximately 10 to 20% are infected through breastfeeding.¹

But with effective HIV treatment and a managed delivery, the risk of mother-to-child transmission (MTCT) can be greatly reduced. Transmission rates fell from about 20% in the UK and Ireland in 1993 to under 2% in 1998, as a result of the introduction of opt-out HIV testing in antenatal care, more extensive use of antiretroviral drugs during pregnancy and delivery, caesarean section for delivery and formula feeding of the baby.

Currently, the risk of mother-to-child transmission in the UK, for women who have been diagnosed and who receive the right advice and treatment is below 1%, with transmission rates for babies of women on combination therapy and a viral load of less than 50 copies/ml at 0.1%.²

Transmission of HIV-2 is less common than transmission of HIV-1. Mothers with HIV-2 are likely to have a lower viral load and slower disease progression. Between 0 and 4% of women with untreated HIV-2 pass on their infection.³