Human immunodeficiency virus type 1 infection and breast milk. The Italian Register for HIV Infection in Children.

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 breast-fed 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.(ABSTRACT TRUNCATED AT 250 WORDS)