An infant's risk of becoming infected with the AIDS virus through
breastfeeding is highest during the first few months of life, according to a
new study conducted among HIV-infected mothers and their babies in the
African nation of Malawi. A mother's inexperience with breastfeeding may
increase HIV transmission risk.
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
NCI and NIAID are components of the National Institutes of Health (NIH).
NCI is the principal federal agency working to prevent cancer and help
patients live longer and healthier lives. NIAID conducts and supports
research to prevent, diagnose and treat illnesses such as HIV disease and
other sexually transmitted diseases, tuberculosis, malaria, asthma and
allergies. NIH is an agency of the U.S. Department of Health and Human
Press releases, fact sheets and other NIAID-related materials are available
on the NIAID Web site at http://www.niaid.nih.gov.
PG Miotti, TET Taha, NI Kumwenda, et al. HIV transmission through
breastfeeding: a study in Malawi. JAMA 282:744-49 (1999).