A new study has found that HIV-infected mothers are less likely to transmit the virus to their newborns if they breastfeed their child exclusively for more than 4 months. The findings have important implications in sub-Saharan Africa, where infants are at greater risk of contracting and dying from diarrheal diseases or pneumonia.
Breastfeeding is widely regarded as the best form of nutrition for newborns because human milk transfers not only essential nutrients but also important immune-system factors from mother to child, protecting the baby against potentially life-threatening infections.
But Louise Kuhn of Columbia University’s Mailman School of Public Health in New York says there has always been some controversy about breastfeeding by HIV-infected mothers, since the virus that causes AIDS can also be transmitted through breast milk.
Public health experts estimate that HIV-infected mothers have a 10 to 15 percent chance of passing the virus to their newborns through their breast milk. Kuhn and her colleagues wanted to find out if changes in breastfeeding routines would affect the levels of HIV in the breast milk.
They studied just over 950 HIV-infected women in Lusaka, Zambia in 2006 - before antiretroviral drugs were given to nursing mothers - and encouraged all of them to exclusively breastfeed their babies from birth for at least 4 months. Throughout the study, the newborns were regularly tested for HIV.
At the 4 month mark, half of the mothers were asked to stop nursing, while the other half continued to breastfeed exclusively. At 4.5 months, Kuhn says samples of breast milk were collected from all of the study participants and analyzed.
“We found that stopping breastfeeding early was a really bad idea for several different reasons," said Kuhn.
Kuhn says investigators discovered the highest concentrations of HIV in the breast milk of women who had stopped breast feeding at 4 months. More than 3/4 of them had evidence of the virus in their milk, compared to just under 40 percent of the women who were still breastfeeding. The two groups of women showed no differences in HIV levels two weeks earlier, when they were both tested at the four-month mark.
Women in a control group who nursed an average of 16 months and supplemented breastfeeding with other nutrition also had higher HIV concentrations in their milk compared to those who breastfed exclusively beyond 4 months.
Investigators believe changes in breast tissue that occur during sudden weaning could account for higher concentrations of HIV in women who stopped nursing at 4 months.
Kuhn says the results show that even subtle decreases in breastfeeding frequency during a child’s infancy can increase concentrations of HIV in an infected mother’s breast milk. That suggests that it is in the interest both of the mother and child for women to practice exclusive and extended breastfeeding.
Kuhn notes that breastfeeding is actually a very inefficient way to transmit the AIDS virus. She says the risk is minimal among mothers who nurse and take antiretroviral drugs at the same time.
“If antiretroviral drugs are given and an HIV-positive woman is fully adherent with the treatment throughout the duration of breastfeeding, the actual risk of transmitting HIV through breast milk is exceedingly low. It’s probably in the 1 to 2 percent [range] if not lower with complete adherence with antiretroviral therapy," she said.
An article on reducing the risk of mother-to-child HIV transmission through breast milk is published in the journal Science Translational Medicine.