August 24, 1999
A report of the study by researchers from the National Institutes of Health, the Johns Hopkins School of Hygiene and Public Health in Baltimore, MD, and the Malawi College of Medicine in Blantyre, Malawi, appears in the August 25 issue of the Journal of the American Medical Association.
"This is a very important area of research," comments Anthony S. Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases (NIAID), which co-funded the study with the National Cancer Institute (NCI). "Little is known about the timing of HIV infection through breastfeeding or the associated risk factors. This finding and other ongoing studies will help HIV-infected women make informed decisions about infant feeding."
Breastfeeding is the recommended method of infant feeding in Malawi and other developing countries, where alternatives to breast milk are often scarce, unsafe or culturally unacceptable. In the United States, where safe alternatives to breast milk are plentiful, HIV-infected women are advised against breastfeeding their infants.
Lead author Paolo Miotti, M.D., of NIAID's Division of AIDS, senior author Robert J. Biggar, M.D., of NCI's Division of Cancer Epidemiology and Genetics, and their colleagues investigated the timing of, and risk factors for, HIV infection among breastfed infants of HIV-infected mothers. The researchers tested infants for HIV infection during visits to the postnatal care clinic of a large urban hospital in Malawi. Only babies who tested negative for HIV at their first visit, six weeks after birth, were included in the study. The researchers' objective was to examine breastfeeding-related HIV infections. Positive HIV tests during the first weeks of life can result from infection that occurred during pregnancy or childbirth as well as through breastfeeding.
Subsequent HIV tests conducted over the next two years revealed that 47 of the 672 infants in the study became HIV-infected from breastfeeding. Nearly half (21) of the infections occurred within five months after birth. Another 15 babies became infected between postnatal months 6 and 11, and seven more between months 12 and 17 of follow-up. Only four HIV infections occurred between months 18 and 23. No babies became infected with HIV after they stopped breastfeeding.
Statistical analyses showed that women who had fewer than four previous births were more likely to transmit HIV through breast milk than were women who had four or more. Similarly, younger mothers were more likely than older mothers to transmit HIV through breast milk.
Drs. Miotti, Biggar and their colleagues speculate that mothers who are relatively less experienced with breastfeeding are more likely to have subclinical mastitis, an inflammation of the mammary tissue, and thereby a higher HIV transmission rate. The researchers note that in another recent study conducted among a separate population of women in Malawi, they found that subclinical mastitis was associated with higher HIV levels in breast milk and higher HIV transmission to breastfeeding infants.
"HIV transmission was highest in the early months, but persisted for as long as infants continued breastfeeding," notes Dr. Miotti. "Early weaning has been proposed as one possible strategy to limit HIV transmission through breast milk," he adds. "Although discontinuing breastfeeding after six months would have prevented half of the HIV infections seen in our study, such an approach would increase the risk for illness and death from the respiratory and diarrheal diseases that antibodies and other factors in breast milk help protect against."
The researchers conclude that breastfeeding recommendations for HIV-infected women in developing countries must carefully balance the risk of HIV transmission with the well-known nutritional and health benefits of breastfeeding. "Recommendations may be most usefully made at the level of the individual mother, since communities in developing countries include women from varied socioeconomic strata who have different access to safe-milk alternatives."
PG Miotti, TET Taha, NI Kumwenda, et al. HIV transmission through breastfeeding: a study in Malawi. JAMA 282:744-49 (1999).
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