Preventing Mother-to-Child Transmission of HIV

Preventing the transmission of HIV from mother to child is an important part of the fight against HIV and AIDS. With the use of highly active antiretroviral therapy (HAART) and good prenatal care, the risk of an infant acquiring HIV from its mother can be reduced significantly.

Testing

An important part of prevention is testing. The U.S. Public Health Service recommends that all pregnant women be tested for HIV, along with several other infections that can affect a developing fetus. It is recommended that this be done as early as possible during pregnancy, and again in the last trimester of pregnancy for women at high risk. Most clinics or centers that provide care for pregnant women practice opt-in testing, meaning that an HIV test will be offered to all pregnant women but can only be done after informed consent has been obtained. The Centers for Disease Control and Prevention (CDC) has recently recommended the Opt-out strategy. With the opt-out approach, HIV testing is done as part of routine screening, along with other baseline prenatal blood work. The patient must be informed that the test is being ordered, and it is only omitted if the patient opts out of testing. Health care providers might also recommend that pregnant women be tested during the third trimester of pregnancy as well, even if their first test was negative. If a woman is in labor and her HIV status is unknown, she can still be tested using a rapid HIV test.

Transmission

If a pregnant woman who is HIV-positive receives no HIV treatment, her risk of passing on the virus to her child is approximately 25%. This risk can be reduced to as low as 1% if a pregnant woman and her health care provider follow the treatment guidelines described in the next section.

Transmission of HIV is most likely to occur late in pregnancy or during delivery. While the fetus is still in-utero, HIV can be transmitted by the mother’s blood entering the fetus’ circulation. HIV can also infect the infant during labor and delivery due to mucosal exposure. Other behaviors that can increase the risk of HIV transmission during pregnancy include smoking, drug use, and unprotected sexual intercourse with multiple partners. The higher a mother’s viral load (the amount of copies of the virus in her blood) is during pregnancy and delivery, the higher the risk of transmitting HIV to her child. Even if an infant is not infected with HIV during pregnancy or delivery, there is an additional risk of transmitting HIV through breastfeeding. If a mother is not on HIV therapy while breastfeeding, the risk of transmission is about 10% to 14%.

Therapy

If a pregnant woman finds out she is HIV-positive, or if she is aware of her HIV status before becoming pregnant, it is highly recommended that she begin or continue HAART. All pregnant women who are HIV-positive should be on some form of antiretroviral therapy, no matter what their CD4+ T-cell count (a measure of the strength of the body’s immune system) or viral load (number of copies of the virus in the blood).

If a woman who is HIV-positive wishes to become pregnant, she should consult with her HIV specialist and obstetrician about beginning or making changes to antiretroviral therapy. Although most antiretroviral medications are safe during pregnancy, it is recommended that some of them be avoided. An HIV specialist will know which medications should not be used during pregnancy. If a woman finds out she is pregnant while taking antiretroviral medications, she should not discontinue these medications until speaking with her HIV specialist. If a woman finds out she is HIV-positive for the first time during her pregnancy, the decision for when to begin antiretroviral therapy depends on what her goals for therapy are. If she chooses to begin therapy for her own health, for example because her CD4+ T-cell count is low, then she should begin therapy as soon as possible. If the decision to begin therapy is based on preventing the transmission of HIV to her infant, then a woman can choose to delay therapy until after the first trimester, in consultation with her HIV specialist.

Zidovudine or AZT is an important part of any antiretroviral regimen for pregnant women. Although using AZT alone has been shown to be effective in reducing the risk of transmission, highly active antiretroviral therapy (HAART) regimens that use a combination of more than one medication are even more effective and are recommended. In many parts of the world, HAART is not easily available or is too expensive. Shorter regimens closer to the date of delivery, with only AZT or with other, less expensive medications like nevirapine, have been tested and can also be effective in reducing the risk of transmission.

Delivery

Zidovudine (AZT) should be given intravenously to HIV-positive pregnant women during labor. It is recommended that some HIV-positive women deliver by Caesarean section (“c-section”) if possible, after weighing the risks and benefits of the procedure.

These are the situations when it is especially important to deliver by Caesarean section:

Viral load of the mother is unknown or greater than 1,000 copies/mL at 36 weeks of pregnancy
No anti-HIV medications have been taken or only AZT has been taken during pregnancy
No prenatal care until 36 weeks into pregnancy or later

It is important to try to reduce the amount of time spent in labor as much as possible, since a prolonged labor and delivery can increase the risk of transmission. Some pregnant women do not find out they are HIV-positive until immediately before or during labor, through the use of a rapid HIV test. Even right before delivery, it is not too late to receive antiretroviral medication, and it is recommended that either AZT alone or in combination with lamivudine (3TC) be given to the mother as soon as possible.

Infant Testing

Infants born to HIV-positive mothers must be tested for HIV themselves. Infants less than 18 months of age will have the same antibodies in their blood as their mother, so any infant born to an HIV-positive mother will have a positive HIV antibody test, even if the infant is HIV-negative. There are HIV tests that look directly for the virus itself, using a technique known as PCR. Occasionally, this test can be negative even if the infant does have HIV, so this test is done at three different times:

Birth to 14 days
1 to 2 months of age
3 to 6 months of age

If an infant tests negative on two of these direct HIV tests, an HIV antibody test will be done at 18 months of age. If the antibody test is negative at this point, the infant does not have HIV. If an infant tests positive on two of the direct HIV tests, it is likely that the infant truly has HIV and should be referred to an HIV specialist.

Infant Therapy

Any infant who is born to an HIV-positive mother should take a short course of antiretroviral medication right after birth until his/her HIV status is determined. The recommended regimen include six weeks of liquid zidovudive (AZT), which can be taken by mouth. The infant should start receiving medication within 6 to 12 hours after birth. Different antiretroviral medications might be used or added to the regimen depending on maternal/infant information and risk. Infants on an AZT medication regimen should have their blood tested to check for anemia, a low blood count, which can be a side effect of the AZT

It is also recommended that all infants born to HIV- positive mothers be given medication to prevent the development of a certain type of lung infection (pneumonia) known as PCP. HIV weakens the immune system, which can make people more likely to get PCP. The recommended medication is trimethoprim-sulfamethoxazole, although others may be used instead. The treatment should be started after the 6 weeks of antiretroviral therapy, and should be continued until the infant’s HIV status is known.

Breastfeeding

Although breastfeeding is usually the best option for a growing infant, in the case of HIV infection it is not necessarily the best choice. The U.S. Centers for Disease Control and Prevention (CDC) recommend that mothers who are HIV-positive not breastfeed if they have access to infant formula. Access to clean drinking water is also important, since many women use powdered forms of infant formula that must be mixed with water. In areas of the world where clean drinking water is not available, or where infant formula is not available or too expensive, the benefits of breastfeeding (increased natural immunity, decreased infections) may outweigh the risk of HIV transmission. This is a decision that each mother must make on her own in consultation with her health care provider.

Sources

CDC Revised Recommendations for HIV Testing of Adults, Adolescents, and Pregnant Women in Health-Care Settings. MMRW 2006; 55(RR14);1-17.
HIV During Pregnancy, Labor and Delivery, and After Birth – Factsheets, AIDSinfo, U.S. Department of Health and Human Services, January 2008.
“HIV Infection in Infants and Children,” The National Institute of Allergy and Infectious Diseases (NIAID), July 2004. http://www.niaid.nih.gov/factsheets/hivchildren.htm
Paintsil, E and Andiman, W. “Care and Management of the Infant of the HIV-1-Infected Mother,” Seminars in Perinatology 2007,31:112-123.

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