Rates of transmission

Prior to the introduction of short-course antiretroviral interventions during labour and delivery, prolonged breastfeeding was associated with less than half of mother-to-child HIV transmissions in the developing world.¹ However, treatment interventions to prevent mother-to-child transmission during pregnancy and childbirth are now commonly used. This means that despite a reduction in mother-to-child HIV transmission, prolonged breastfeeding may become the leading cause of HIV infection in infants.

Overall, an estimated 5 to 20% of infants from HIV-positive mothers are infected postpartum and the risk increases as breastfeeding continues. A randomised clinical trial of 425 women in Nairobi reported that without short-course antiretroviral treatment, breastfeeding for two years or more doubles the overall risk of mother-to-child transmission of HIV to about 40%.² It should be kept in mind though, that in the absence of a sanitary water supply, roughly the same percentage of children will die from gastrointestinal illness.

Another study of pooled data from mother-to-child transmission studies of over 1500 infants found that 12% born to HIV-positive mothers contracted HIV infection via breast milk.³. A Tanzanian study showed that infants who are not infected at birth have a 4% risk of contracting HIV at four months and an 18% risk of HIV infection at two years. This risk is increased by high maternal viral load and low CD4 cell counts.⁴.