How is HIV/AIDS spread to children and infants?

HIV-infected mothers run the risk of transmitting HIV to their infants during pregnancy, labor, delivery, or breastfeeding. Almost all HIV-infected children and infants acquire HIV from their mothers before or during birth or through breast-feeding. In the U.S., approximately 23 percent of pregnant, HIV-infected women not receiving any antiretrovirals (drugs used to treat HIV/AIDS) and not breastfeeding have passed HIV to their babies. The rate of transmission between mothers and children is significantly higher in developing countries than it is in the U.S., partially because women in developing countries are more likely to breast-feed.

Prior to 1985, when screening of the U.S. blood supply for HIV began, some children and adults were infected with HIV through transfusions of blood or blood products contaminated with HIV. A smaller number of children also have been infected with HIV through sexual or physical abuse by HIV-infected adults.

What is the role of pregnancy and birth in the transmission of HIV/AIDS?

Mother-to-child transmission (MTCT) causes more than 90% of HIV infections worldwide in infants and children. Although the precise mechanisms are unknown, scientists know HIV may be transmitted before delivery. The role of the placenta in maternal-fetal transmission is unclear and is the focus of ongoing research. HIV may also be transmitted during labor and delivery by mucosal exposure to HIV.

The risk of MTCT of HIV increases significantly if the mother has advanced HIV disease, increased levels of HIV in her bloodstream, or fewer numbers of the immune system cells (CD4 cells)—the main target of HIV.

Other factors that may increase the risk of MTCT include: maternal drug use, severe inflammation of fetal membranes, or a longer period between membrane rupture and delivery.

What is the role of breastfeeding in transmission of HIV from mother to infant?

HIV also may be transmitted from a nursing mother to her infant. Studies have suggested that breastfeeding introduces an additional risk of HIV transmission of approximately 10 to 14 percent among women with chronic HIV infection. In developing countries, an estimated one-third to one-half of all HIV infections are transmitted through breastfeeding.

The World Health Organization recommends that all HIV-infected women be advised of both the risks and benefits of breastfeeding their infants. In situations in which safe alternatives to breastfeeding are readily available and economically feasible, exclusive formula feeding should be encouraged. In general, in developing countries where safe alternatives to breastfeeding are not readily available, exclusive breastfeeding should be encouraged. The benefits of breastfeeding in terms of decreased illness and death due to other infectious diseases greatly outweigh the potential risk of HIV transmission.

What is being done to prevent transmission from mother to child?

In 1994, a landmark study conducted by the Pediatric AIDS Clinical Trials Group (PACTG) demonstrated that zidovudine (AZT), a drug used to prevent MTCT of HIV, given to HIV-infected women who had very little or no prior antiretroviral therapy, reduced the risk of MTCT by two-thirds, from 23% to 8%. In the study, AZT therapy was initiated in the second or third trimester of pregnancy and continued during labor. In addition, infants were treated for six weeks following birth. AZT produced no serious side effects in mothers or infants. Long-term follow-up of the infants and mothers is ongoing.

A few years later, another PACTG study showed that the risk of transmitting HIV from an HIV-infected mother to her newborn infant could be reduced to 1.5% among women who received antiretroviral therapy (ART), a combination of drugs used to treat HIV/AIDS, and appropriate medical and obstetrical care during pregnancy.

In September 1999, HIVNET 012, a trial to determine the efficacy of AZT and the efficacy of nevirapine (NVP), a drug used to prevent MTCT, for the prevention of MTCT of HIV in pregnant Ugandan women and their babies, was completed. This study demonstrated that single doses of NVP given to the mother and to the infant lowered the risk of HIV transmission during the first 14 to 16 weeks of life by nearly 50% when compared to AZT. Furthermore, the results were sustained after 18 months. This simple, inexpensive regimen offers a potentially cost-effective alternative for decreasing MTCT in developing countries.

In addition, in April 1999, the International Perinatal HIV Group reported that elective caesarian section (c-section) delivery can reduce MTCT of HIV, though it is not without risk to certain women. In the developed world, where effective therapy is available, c-section delivery is recommended in specific circumstances for women living with HIV. But elective c-section is not a viable option for most HIV-infected pregnant women in the developing world.

What is the rate of disease progression in infants and children?

There are two patterns of illness in HIV-infected children: those whose illness progresses more rapidly and those whose illness progresses more slowly. In the developed world, 20% of children develop serious illness rapidly and will die by four years of age. The remainder of the population lives longer and the mortality is approximately 10% per year. The same dichotomy exists in the developing world, but many more children experience rapid progression of disease. An observed 35% of children with HIV die by the time they are one year old, 50% die by age two, and 60% die by age three.