Although there is a 10 to 15 percent risk of HIV transmission from breastfeeding, Columbia University's Mailman School of Health found that extended breastfeeding actually reduced the chances of the transmission.
The study looked at almost 1,000 HIV-infected mothers in Zambia. Half of them breastfed for four months, and others breastfed beyond that; all were advised to breastfeed exclusively. In the mothers who practiced extended breastfeeding, less than 40 percent had HIV present in their milk at four and a half months; at the same time, more than 75 percent of mothers who stopped breastfeeding had HIV in their milk.
Study author Louise Kuhn said that, if antiretroviral drugs are given in conjunction with extended breastfeeding, the overall risk of HIV transmission would be very low: "It’s probably in the one to two percent [range] if not lower with complete adherence with antiretroviral therapy," Kuhn said.