Mother-to-child transmission (MTCT) of HIV refers to the spread of the Human Immunodeficiency Virus from a woman living with HIV to her child. This transmission can occur during pregnancy, childbirth, or through breastfeeding. Without interventions, the risk of transmission can range from 15% to 45%. Substantial advancements in prevention and treatment have dramatically altered the landscape of pediatric HIV, leading to a significant reduction in new infections.
How Transmission Occurs
HIV can be transmitted from a mother to her child during three distinct periods.
The first period is during pregnancy, where the virus can cross the placenta to the developing fetus. While this can occur at any point, studies suggest that approximately 80% of transmissions happen during late pregnancy, specifically from 36 weeks until labor.
The second period is during labor and delivery. As the baby passes through the birth canal, it can be exposed to the mother’s blood, vaginal fluids, and other bodily secretions containing the virus. This exposure is the most common route for MTCT, accounting for over 50% of cases without intervention. Factors like prolonged rupture of membranes or obstetric procedures can increase this risk.
The third mode of transmission occurs through breastfeeding. HIV can be present in breast milk and passed to the infant during feeding. Breastfeeding can account for an additional 10-20% transmission risk, and prolonged breastfeeding further increases this risk. Exclusive breastfeeding carries a lower risk than mixed feeding.
Preventing Transmission
Preventing mother-to-child transmission of HIV involves a multi-faceted approach, with antiretroviral therapy (ART) for the mother being a primary strategy. ART significantly reduces the amount of HIV in the mother’s body, known as the viral load, thereby lowering the risk of transmission during pregnancy, labor, and breastfeeding. Early diagnosis of HIV in pregnant women and prompt initiation of ART are important steps in achieving viral suppression, meaning the viral load is so low it cannot be detected.
Management during labor and delivery also plays a role in prevention. For mothers with an undetectable viral load, a vaginal delivery is generally safe. However, if the mother’s HIV is untreated or her viral load is above 1,000 copies/mL near delivery, a planned cesarean section (C-section) can help reduce the risk of transmission. Additionally, administration of ART to the mother during labor provides further protection to the infant.
Infant prophylaxis involves administering ART to newborns of HIV-positive mothers shortly after birth. This preventative treatment is given for two to six weeks to protect against any potential exposure to the virus during delivery. This intervention significantly contributes to reducing the overall transmission risk to less than 1% when combined with maternal ART.
Infant feeding choices are also carefully considered to prevent transmission. For mothers on ART with a suppressed viral load, breastfeeding carries a very low risk of transmission, typically less than 1%. However, the risk is not entirely eliminated. In situations where safe and feasible, infant formula or banked donor human breast milk are alternative options that completely eliminate the risk of transmission through breastfeeding.
Testing and Monitoring for Mother and Child
Maternal HIV testing during pregnancy is a cornerstone of prevention efforts. Routine HIV screening is recommended for all pregnant women, ideally during their first prenatal visit. Early detection allows for the prompt initiation of antiretroviral therapy, which is crucial for reducing the risk of transmission. For women with an unknown HIV status who present in labor, rapid HIV testing is recommended to allow for immediate interventions if needed.
Infants born to HIV-positive mothers undergo specific HIV testing to determine their status. Standard antibody tests are not used for newborns because maternal HIV antibodies can cross the placenta, leading to a positive antibody test result even if the infant is not infected. Instead, virologic tests, such as PCR, are used to directly detect the presence of the virus in the infant’s blood. These tests are typically performed at specific intervals: at birth or within the first 14 days, again at 1 to 2 months, and a final test at 4 to 6 months of age.
Ongoing monitoring and care are important for both the mother and the infant. The mother continues to receive medical care for her own HIV management, ensuring viral suppression and overall health. For the infant, even if uninfected, follow-up testing and general health monitoring are provided to ensure their well-being and to confirm their HIV-negative status at 12 to 18 months of age using an antibody test.
Global Progress in Eliminating Transmission
Significant global achievements have been made in reducing mother-to-child transmission rates due to widespread implementation of prevention strategies. New HIV infections among children under five years of age have dramatically declined, with an estimated 120,000 new infections in 2024, representing a 62% decrease from 310,000 in 2010. This progress is largely attributed to increased access to prevention of mother-to-child transmission (PMTCT) services and the initiation of lifelong antiretroviral medicines for pregnant women living with HIV.
The “Global Plan towards the Elimination of New HIV Infections among Children and Keeping their Mothers Alive,” launched in 2011, set ambitious targets. The accelerated rollout of highly effective, simplified interventions based on lifelong ART for pregnant women living with HIV has demonstrated the feasibility of virtual elimination of MTCT. Several countries have achieved transmission rates below 5%, moving towards the criteria for elimination.
Despite this progress, challenges persist in some regions, and continued efforts are needed to reach the 2030 targets set by UNAIDS. The World Health Organization (WHO) continues to promote the integration of PMTCT interventions into maternal, newborn, child, and adolescent health services, alongside strengthened health systems. This includes improved access to sexual and reproductive health services and screening for sexually transmitted infections, all contributing to the global goal of eliminating MTCT.