HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INFECTION AND BREAST-MILK

Major questions are whether mothers infected with the Human Immunodeficiency Virus type 1 (HIV-1) transmit the virus through breast milk and the magnitude of the additional transmission risk. The demonstration of a dose-response effect is an epidemiological method to demonstrate causality. Thus, a study was carried out by the Italian Register for HIV Infection in Children on 961 children of known infection status. Duration of breast-feeding was considered as the level of exposure in 168 ever breastfed children. Results showed that duration of practice significantly increased the risk of transmission. The adjusted infection odds ratio for one day of breast- versus exclusive formula-feeding was 1.19 with narrow confidence limits (1.10-1.28). In a second study by the Register on 556 children of known infection status and derived prospectively, an infection odds ratio of 2.55 (confidence interval: 1.03-6.37) was calculated in breast- versus exclusively formula-fed children. Several lines of evidence, including the above-mentioned data from the Italian Register for HIV Infection in Children, showed a contribution of breast-feeding to mother-to-child HIV-1 transmission. Thus, this practice is now discouraged in HIV-1 infected mothers living in industrialized societies where formula feeding is practical and attainable. Mode of feeding was known in 2183 children enrolled in the Register and born to HIV-1 infected mothers since 1981. It could be observed that feeding habits of at-risk infants changed in Italy in the middle 1980s, when a large majority of subjects was identified at birth. However, women infected exclusively by the sexual route are often unconscious of being infected or even being at risk from infection and consequently their children are less frequently identified at birth than are children of women with a history of intravenous drug use. In industrialized areas, the former children remain at risk from milk-borne HIV-1 infection.