How does antiretroviral therapy reduce mother-to-child HIV transmission?

Antiretroviral therapy (ART) significantly reduces the risk of mother-to-child HIV transmission—also known as vertical or perinatal transmission—by suppressing the amount of virus present in the mother's blood, known as the viral load.12

When an HIV-positive woman takes antiretroviral drugs during pregnancy and at the time of delivery, the medication works to inhibit viral replication. Specifically, drugs like AZT function by interfering with the reverse transcriptase enzyme, which the virus requires to replicate its genetic material and infect host cells. By lowering the concentration of the virus in the mother's system, the likelihood of the virus passing to the infant during pregnancy, labor, or delivery is substantially reduced, often to less than 2 percent.123

Additionally, administering antiretroviral therapy to the newborn for several weeks after birth further decreases the risk of transmission. When combined with practices such as formula feeding—which avoids the risk of transmission through breast-feeding—these interventions are highly effective at preventing pediatric HIV infection.1