Contribution of breastfeeding to the reported variation in rates of mother-to-child HIV transmission

Abstract

In a recent article on mother-to-child transmission (MCT) of human immunodeficiency virus type 1 (HIV-1) in the Congo Lallemant and colleagues reported a 40.4% MCT rate in the Congo and attributed the seroconversion of 3 additional children who were seronegative at 12-15 months to breastfeeding; however these infants were excluded from the calculation of MCT rate. These cases were discovered only because seroconversion occurred after maternal antibody had been lost. Since current technology does not distinguish between children who were infected in the early postnatal period (when maternal antibody was still present) and those who were infected at birth the 3 infants represent a minimal estimate of the number of children in their cohort who were postnatally infected. The accompanying editorial by Ryder and Behets discussed reasons for the wide variation in reported rates of MCT without mentioning breastfeeding as a potential transmission route and restricted their definition of postpartum MCT to the period occurring immediately after birth. Although the observed variation in reported MCT rates may be accounted for by the clinical and nutritional status of pregnant women methodologic variations in MCT studies selection biases or differential transmission of different HIV variants transmission through breast milk has been well documented. Growing numbers of children have seroconverted after losing passively transferred maternal antibody according to these studies. A meta-analysis examining MCT through breast milk estimated the risk of transmission to be 14%. This is of particular importance in formulating policy in the developing world. Future investigations should monitor any breast fed child with antibody testing for at least 24 months or until at least 3 months after cessation of breastfeeding. All children infected by any route of MCT should be included in MCT transmission rate calculations. Polymerase chain reaction genetic sequencing and other molecular techniques should be used in ascertaining the time at which MCT occurs.