HIV concentrations in breast milk higher at earlier, abrupt weaning

HIV-infected mothers who breast-fed exclusively longer than the first four months after birth had less risk of transmitting the virus to their babies through their milk, researchers said.

To test whether breast-feeding routines affect the levels of HIV in breast milk, the researchers tested nearly 1,000 women and their infants in Lusaka, Zambia, over 24 months. The women were divided into two groups – one that weaned their babies abruptly after four months, and one in which the women continued to breast feed as long as they chose.

At 4 1/2 months, the HIV concentrations in breast milk were “substantially higher” in the group that weaned than in the group that continued to nurse their children. And among those who kept nursing, the HIV levels were higher among women who did not do so exclusively, the researchers wrote. And, they said, the results are conservative, because only 60.5% of the women who were to wean their children actually did so by 4 1/2 months.

“Our results have profound implications for prevention of mother-to child HIV transmission programs in settings where breast-feeding is necessary to protect infant and maternal health,” the researchers from Columbia University wrote. The results were published Wednesday online in the journal Science Translational Medicine.

HIV-infected women typically have a 10% to 15% chance of transmitting the virus to their babies through breast milk. But in sub-Saharan Africa, nursing is an important way to help children develop immunities to fight many infectious diseases.

The researchers said the explanation could be the opening of the paracellular tight junctions of the mammary gland, which occurs during the establishment of lactation and during weaning.

More than three-quarters of the women who stopped breast feeding at four months had detectable concentrations of HIV in their breast milk, compared with 39.5% of those exclusively breastfeeding at 4 1/2 months. The women had showed no differences in the levels at four months.

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