A study by scientists at the Africa Centre for Health and Population Studies, South Africa, has shown that exclusive breastfeeding can significantly reduce the risk of HIV transmission from mother to child in infants aged under six months when compared to those also given solid foods or replacement feed (i.e. formula milk).
The research, published today in The Lancet, has implications for people in resource poor settings, such as in rural Africa.
In the study, funded by the UK's Wellcome Trust, researchers at the Africa Centre, University of KwaZulu-Natal, found that there was a 4% risk of postnatal transmission to infants solely fed on breast milk between the age of 6 weeks and 6 months of age. Infants who received formula milk or animal milk in addition to breast milk were nearly twice as likely to be infected as infants who received breast milk only. More alarmingly, those given solids in addition to breast milk were almost eleven times more likely to acquire infection.
"The question of whether or not to breastfeed is not a straightforward one," says Professor Hoosen Coovadia from the Africa Centre. "We know that breastfeeding carries with it a risk of transmitting HIV infection from mother to child, but breastfeeding remains a key intervention to reduce mortality. In many areas of Africa where poverty is endemic, replacement feed, such as formula milk or animal milk, is expensive and cannot act as a complete substitute. The key is to find ways of making breastfeeding safe."
In the developed world, the risk of transmission of HIV from mother to child has been dramatically reduced from about 25% to less than 2% thanks to the use of antiretroviral therapies, exclusive formula feeding regimes and excellent healthcare systems, but these are not available in resource-poor areas.
The mucous membrane within the intestine is thought to act as an effective barrier to HIV infection. Breast milk ordinarily strengthens and protects this lining. Exclusive breastfeeding is also associated with fewer breast health problems such as mastitis and breast abscesses, both of which can increase the amount of the HIV virus in the mother's breastmilk. It is unclear why adding solids may be particularly hazardous, though previous research has suggested that the larger, more complex proteins found in solid foods may lead to greater damage to the lining of the stomach, allowing the virus to pass through the gut wall.
Professor Coovadia and colleagues also found a significant increase in the risk of transmission even amongst exclusively breastfed infants when the mother had a CD4 cell count of less than 200/ml. CD4 cells coordinate the immune systems response to infection. Compared to mothers with a CD4 cell count of 500/ml, mothers with a CD4 count of less than 200/ml were almost twice as likely to infect their infants.
In addition to studying the risks of transmission, trained lay workers offered counselling to HIV-infected mothers to improve exclusive breastfeeding practices. As a result, they were able to achieve a much higher rate of exclusive breastfeeding than previously reported in similar communities.
The validity and importance of the results have been strengthened by other recently published and ongoing studies in Africa which confirm the team's findings about reduced transmission of HIV with exclusive breastfeeding, and the dangers to infant health and survival when replacement feeding deprives babies of the protective shield of breast milk.
"Based on our findings and evidence of being able to successfully support exclusive breastfeeding in HIV-infected women, and recent data from other parts of Africa, we believe that current guidelines on infant feeding warrant revising," says Professor Coovadia. "Previous reports have confused rather than guided such policies and we hope that our study will help clarify this complex issue."