Breastfeeding does not contribute to mortality among HIV-positive mothers in Kenya

A prospective cohort study has found that HIV-positive Kenyan mothers who breastfed their babies had faster declines in CD4 cell count and body mass index than those who formula-fed. However, breastfeeding had no effect on viral load or overall mortality among the mothers after two years.

Most discussion of breastfeeding by HIV-positive mothers focuses on the risk of HIV transmission to the baby. Several studies have now looked at the consequences for the mother in African settings where breastfeeding is common. The first such study, a randomised clinical trial in Kenya, found an increased risk of mortality for breastfeeding mothers compared to those who formula-fed. However, four subsequent African cohort studies found no such association.

Now, a prospective cohort study by the original study team, published in the January 15^th edition of the Journal of Infectious Diseseases has found faster CD4 cell count declines in breastfeeding mothers, but no increase in mortality over a two-year period.

The study, conducted through the Kenya Medical Research Institute and the University of Nairobi, looked at 296 HIV-positive new mothers between October 2000 and June 2005. Ninety-eight of the women chose to formula-feed their babies, and 198 breastfed. The groups were not randomised and were not completely comparable – more of the formula-feeding mothers had post-primary education (59% vs. 36%), had flush toilets (66% vs. 44%), and had had HIV-related illnesses (29% vs. 18%). Otherwise, the groups were similar at baseline (measured at 32 weeks of pregnancy) – median age 25 years, mostly (90%) married, mean CD4 cell count of 466 cells/mm³, mean HIV viral load of 4.7 log₁₀. All women were given “standard antenatal care as well as short-course zidovudine [AZT]” according to the CDC Thai regimen.

Follow-up was done at the time of delivery, then monthly for a year and at three-to-four month intervals for the second year after delivery. (Women who started antiretroviral therapy or had a second pregnancy were not included.) As expected, there was a small decline in HIV viral load (to 4.0 log₁₀) due to AZT treatment at the time of birth. Over the next two years, CD4 cell counts declined by an average of 7.7 cells/mm³ per month for women who were actively breastfeeding, and by 4.4 cells/mm³ per month for the women who were not (P =. 014). CD4 cell counts continued to fall, but less rapidly, in women who were breastfeeding but then stopped – reaching levels of decline (3.2 cells/mm³/month) similar to women who had never breastfed.

Over the two years of follow-up, there were twelve deaths (6%) among the women who ever breastfed (eight from HIV-related causes), and four (4%) among those who never breastfed. The risk of death was associated with baseline CD4 cell count (P

Researchers concluded that “there were significant differences in CD4 cell count decline and BMI [body mass index] between breastfeeding and non-breastfeeding women but no differences in HIV-1 RNA levels or mortality over the two-year postpartum period. Thus, although lactation appeared to have effects on CD4 cell count, there were no long-term effects of lactation on either HIV-1 RNA level or mortality.” These findings were “consistent with the findings of other observational studies”, and may explain the group’s own observation, in an earlier study, of “increased mortality in a randomised clinical trial”.

An accompanying commentary notes “the preponderance of evidence [now] indicates that HIV-infected mothers are not compromised by breastfeeding their infants.” Also, since formula-fed infants are in fact more likely to die of causes other than HIV, “replacement feeding [does] reduce HIV transmission to infants, [but] at the cost of creating substantial additional risks … and [does] not reduce overall infant mortality.” As breastfeeding is “nutritionally optimal for all infants” and “not found to be associated with increased maternal morbidity or mortality when appropriate care [is] available”, the authors suggest that the current recommendations for infant feeding in resource-poor settings be reviewed and revised to reflect new findings.