How Breast Milk Can Transmit HIV and Why We Should Inform Women


As one of the last fluids we think about when we think about HIV, I thought it might be helpful for us to learn a little more about the 4th fluid that transmits HIV. Since blood, semen and vaginal secretions have gotten all the attention, why not take a moment and learn a little more about how breast milk can transmit HIV.

What a brief review of the research shows:

  • Infant feeding is estimated to be responsible for anywhere from 5-20% of mother to child transmission. If a child is born HIV-negative to a positive mother who is not on antiretroviral treatment, the risk associated with prolonged breastfeeding is estimated at 10-20%.
  • HIV RNA is found in breast milk and the risk of transmission is directly related to the viral load in the mother’s milk.  Some mothers may have a specific gene (SDF1 3’A allele) that causes increased viral replication in breast milk and therefore increases transmission risk.
  • Although breastfeeding from an HIV-positive mother poses a risk of HIV transmission to the infant, there is also evidence that it provides better health outcomes for the child than formula feeding (protective against other infectious diseases)
  • The World Health Organization promotes alternative (formula feeding) only when it is  “affordable, feasible, acceptable, sustainable and safe.” When ARVs are widely available and breastfeeding is a social norm, they recommend that HIV-positive mothers breastfeed until 12 months of age.
  • Women who are on antiretroviral treatment while breastfeeding have a lower risk of transmitting HIV to their infant. (about 3.5% in one study in Kenya)
  • Exclusive breastfeeding has been associated with a reduced risk of late HIV transmission as compared to mixed feeding. Mixed feeding practices (breast milk plus other liquids or solids) and prolonged breastfeeding (more than 6 months) are associated with increased risk of mother-to-child transmission of HIV.
  • Exclusive breastfeeding is hard. Barriers include low milk production, lack of control over the feeding situation, and both perceived and enacted stigma.
  • Infants can develop resistance to HIV medications independent their mother’s resistance – that is, the mother is not necessarily passing on a resistant virus, but if the infant becomes infected while breastfeeding and the mother is on ARV, the infant is being exposed to small amounts of the drugs through breast milk and may therefore develop resistance to them.

The more we can inform women about the risks and benefits associated with breastfeeding, as well as things that can reduce the risk, the better able they will be to make the best decision for themselves and their infants.

Some of the articles/abstracts, if you want to read more in-depth:

WHO Guidelines:

A systematic review of a number of publications on HIV and breastfeeding:

How genetics may impact transmission rates:

Drug resistance:

Large Breastfeeding study in Kenya:

Difficulties of exclusive breastfeeding:

Viral load:

If anyone is still reading,

To kill HIV in breast milk, flash-heating breast milk can inactivate HIV without destroying too many of the vitamins or immunoglobulin in the milk that make it beneficial to the baby. The WHO recommends it as an option to reduce vertical HIV transmission in resource-poor regions. Of course, to do this the mother has to express the milk first, then heat it, then feed it via bottle – so it’s kind of a compromise between breastfeeding, which could transmit HIV, and bottle feeding formula, which has other nutritional/gastrointestinal risks.

What do you think? How has this changed how you think about HIV? Has it changed any of your thoughts?

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