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The data from a trial conducted in South Africa are so compelling that they have helped drive an overhaul of the UN's World Health Organization (WHO) guidelines on HIV prevention for newborns.
Promotion of breastfeeding is a major dilemma for Aids policymakers.Normally, breastfeeding is universally recommended for infants, as breast milk contains vital nutrients that cannot be found in replacement food.
In addition, in poor countries where water supplies may be tainted, a child can be exposed to potentially fatal diarrhoea by taking infant formula, or to malnutrition if the replacement food is poor in vitamins and proteins.
Milk may transmit HIV
But in the case of HIV-positive mothers, breastfeeding may also
pass on HIV to the infant.
Until now, this risk of post-natal transmission has been evaluated as being very high - at between 10 and 20 percent.
According to the agency UNAIDS, each year more than 300 000 children become infected with HIV after they are born.
But the new paper says that the risk estimates do not distinguish between exclusive breastfeeding and mixed feeding.
Under mixed feeding, a child is partly breastfed and partly fed with infant formula or solid food.
Two South African researchers have carried out the first trial to focus primarily on this question.
How the study was conducted
They recruited pregnant women who attended ante-natal clinics in
KwaZulu-Natal, the province with the highest HIV infection rates. Most of
the women were assigned to a group that exclusively breastfed their
babies, and were given counselling.
The others were assigned either to a mixed feeding group or to an exclusively replacement feeding group, and were also given support.
After three months, the HIV infection rate among the exclusively breastfed group was 4.04%.
Significant risk variations
Among the mixed group, babies who received formula milk in
addition to breast milk were twice as likely to be infected with HIV. Those who had solid food - typically porridge -
ran 11 times the risk of infection compared with the
breastfeeding-only group.
In addition, the death rate at three months among the exclusively breastfed babies was 6.1%, while among children given replacement feeds, it was 15.1%.
Reasons still unclear
One of the lead authors, Nigel Rollins of the University of
KwaZulu-Natal, said the reasons why mixed feeding posed a greater
risk of infection were open to investigation.
One possible cause is that foreign proteins found in formula milk increase the vulnerability of the infant gut to HIV, he said.
A total of 1 372 infants took part in the study, 83% of whom were in the exclusive breast-feeding group.
The paper is one of three large studies that were scrutinised by a WHO expert panel last October that recommended changes to the WHO's breastfeeding guidelines established in 2000.
The guidelines call for HIV-infected women to exclusively breast-feed their baby for the first six months unless good, safe, affordable replacement feed is available.
When this replacement feeding is available, the mother must stop breastfeeding in order to block the risk of infection. – (Sapa-AFP)
Read more:
HIV/Aids Centre
March 2007
