Mother-to-Child Transmission (MTCT)

A woman infected with HIV can pass the virus to her baby during pregnancy, labor and delivery, or breastfeeding.

Roughly 15 to 30% of newborns of untreated HIV-positive women will become infected with HIV during pregnancy and delivery and an additional 10 to 20% during breastfeeding. The risk has varied by region—with rates of 15 to 25% transmission in industrialized countries of Western Europe and the U.S., but higher rates (25 to 35%) reported from developing countries. Some studies have found rates as high as 43% in Sub-Saharan Africa. These rates represent the risk for transmission without preventive intervention (see “Preventing HIV Transmission” for information on prevention of MTCT). Treatment options are now available in some settings that can greatly reduce the rate of HIV transmission from mother to child.

The risk for HIV transmission from breastfeeding, which has been estimated to be between 10 and 20%, increases with a longer duration of breastfeeding. The risk for HIV infection through breastfeeding appears to be greatest in the first few months of life and is lower among infants who are fed breast milk exclusively than among those who are breastfed and also receive supplemental foods or liquids. In a recent study in South Africa, babies who were exclusively breastfed were significantly less likely to become infected in the first three months than were those who had mixed feeding.

The risk for HIV transmission from an individual woman to her child is affected by a variety of factors, including:

• Stage of infection: If a woman is later along in her infection, she will have a higher viral load and will be more likely to transmit the virus to the child. Also, if she becomes infected during or just before pregnancy, the initial spike in viral load at the time of infection may increase the risk of MTCT.
• Breastfeeding pattern: Exclusive breastfeeding has been found to present a decreased risk over mixed feeding, which is the norm in many countries.
• Duration of breastfeeding: Risk increases with the duration of breastfeeding (see “Preventing HIV Transmission” for further information).
• Oral or breast lesions: Oral lesions in the baby or lesions on the mother’s breasts increase the risk for transmission due to the increased portals of entry for the virus and exposure to blood.
• Gastrointestinal illness: A weakened gut may increase portals of entry for the virus found in breast milk in a baby who is breastfeeding.
• Antiretroviral therapy: This can significantly reduce the risk for MTCT during pregnancy and labor and delivery.
• Cesarean section: This can significantly reduce the risk for MTCT, but it is technically and financially intensive, and not necessarily realistic in resource-poor settings.
• Invasive procedures: Avoidance of invasive procedures during delivery can significantly reduce risk for MTCT.

It is important to note that all children born to HIV-positive women will test positive for HIV antibodies at birth, whether or not the children are actually infected. This is due to the presence of the mothers’ antibodies in the children’s blood. Antibody testing can accurately determine infection after the age of 18 months.

Facts about mother-to-child transmission

• The risk for HIV transmission during pregnancy is estimated at 5 to 10%, during labor and delivery at 10 to 20%, and during breastfeeding at 10 to 20%.
• When no preventive measures are taken, the overall risk for transmission among women with HIV is estimated at approximately 15 to 35%.
• The risk for transmission will increase if a woman becomes infected or reinfected with HIV during pregnancy or while breastfeeding, or if she develops AIDS, because of the higher viral loads. Viral, bacterial, or parasitic placental infections may also increase the risk for transmission.
• If a woman becomes infected with HIV while breastfeeding, the risk for MTCT will increase.

(More information on mother-to-child transmission and interventions appears in the “Preventing HIV Transmission” module of this course.)

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