| Analysis Shows Infants of Mothers Infected
With HIV Face Nearly Constant Risk For HIV Infection For Duration
Previously, Researchers Thought Risk Diminished As Infants Grew Older
After four weeks of age, infants who breast feed from mothers
infected with HIV continue to be at risk for infection with HIV
for as long as they breastfeed, according to an analysis conducted
and funded by the National Institute of Child Health and Human Development
of the National Institutes of Health. Previously, researchers thought
the risk for being infected with the virus from breast milk diminished
as an infant grew older.
The analysis determined that a significant proportion of infants 42
percent were infected by breast feeding after they were 4 weeks
The study also found that infants were at greater risk for contracting
the virus through breastfeeding if their mothers had low levels
of CD4+ cells, an immune cell targeted by the AIDS virus. Moreover,
male infants were more likely to contract the virus through breastfeeding
than were female infants.
The analysis was conducted by NICHD and the Ghent Working Group
on HIV in Women and Children, appears in the June 15 issue of The
Journal of Infectious Diseases.
"In many poor countries, mothers who are infected with HIV
don't have the option of bottle feeding their infants to prevent
spreading the virus to them," said Duane Alexander, M.D., Director
of the NICHD. "This information will help us to devise new
ways to help prevent infants from becoming infected with the AIDS
In developed countries like the United States, mothers infected
with HIV are generally advised not to breast feed their infants.
The analysis pooled information from a number of studies that took
place in Africa, said the NICHD author of the study, Jennifer Read,
M.D., M.P.H., of NICHD's Pediatric Adolescent and Maternal AIDS
Branch. Dr. Read explained that one of the greatest strengths of
the study was the large number of children included in the analysis.
Taken together, the number of children in the study was much larger
than in any of the studies that attempted to address the issue previously.
All of the studies included in the larger analysis regularly assessed
the infants' feeding patterns as well as their HIV infection status,
beginning shortly after birth
For the analysis, researchers examined information on 4,085 children
in 9 studies. A total of 3,025 children in the study had negative
HIV test results at 4 weeks of age and were breastfed through at
least 28 days of age. Of these 3,025 children, 223 had late postnatal
transmission testing negative for HIV at 4 weeks of age, but testing
positive after that time. The remainder of the 3,025 children who
were uninfected at 4 weeks of age did not become infected.
Late postnatal infections occurred throughout the duration of breastfeeding,
with children becoming infected at any time, from when they were
4 weeks old until they were 18 months old. In all, late postnatal
transmissions occurred among 42 percent of the 993 children for
whom timing of HIV infection was known.
The analysis also revealed that children of mothers who had low
levels of CD4+ cells were more likely to become infected with HIV
than were children whose mothers had higher CD4+ levels.
"The association of lower maternal CD4+ counts and a higher
risk of transmission was not unexpected," Dr. Read said. "Individuals
with lower CD4+ counts may have higher concentrations of HIV in
the bloodstream and in breastmilk."
The researchers do not know why male infants were more likely to
develop late postnatal infections than female infants were. A possible
explanation is that, due to gender differences in immune functioning,
girls are less susceptible to the infection after 4 weeks of age
than are boys. The researchers wrote that other studies have found
that the immune systems of infected male infants vary somewhat from
the immune systems of infected female infants.
According to Dr. Read, the study findings might be useful in devising
new strategies to prevent infected mothers from passing HIV to their
infants through breast milk. Such strategies are essential, she
said, as many women in poor countries don't have the option of formula
feeding their infants. In some areas, formula may be too expensive
for women to afford. Other areas may lack clean water, and mixing
formula with local water may place infants at greater risk of contracting
often times fatal diarrheal diseases. In other areas, it may be
socially unacceptable for women not to breast feed their infants.
In such areas, she explained, choosing not to breast feed or any
other sign that a woman is infected with HIV may result in adverse
consequences for the woman, such as being the victim of domestic
The researchers discussed possible strategies for preventing the
virus from spreading through breast milk, such as giving anti-HIV
drugs to mothers who are breast feeding. Similarly, such drugs might
be given to infants while they are breast feeding.
"An important implication of our analyses is that, since children
of HIV-1-infected mothers have a consistent and substantial risk
of acquisition of HIV-1 throughout the period of breast-feeding,
to be most effective, interventions to prevent transmission through
breast-feeding should be continued until the cessation of breast-feeding,"
the researchers wrote.
The NICHD is part of the National Institutes of Health (NIH),
the biomedical research arm of the federal government. NIH is an
agency of the U.S. Department of Health and Human Services. The
NICHD sponsors research on development, before and after birth;
maternal, child, and family health; reproductive biology and population
issues; and medical rehabilitation. NICHD publications, as well
as information about the Institute, are available from the NICHD
Web site, http://www.nichd.nih.gov,
or from the NICHD Information Resource Center, 1-800-370-2943; e-mail