MOTHER-TO-CHILD TRANSMISSION OF HIV - IMPLICATIONS OF VARIATION IN MATERNAL INFECTIVITY

Objectives: To examine the implications of variation in maternal infec tivity on the timing of mother to-child HIV transmission through breas tfeeding. Design and methods: A mathematical model of mother-to-child HIV transmission was developed that incorporates two main features: (i ) the fetus/child potentially experiences a series oi exposures (in ut ero, intrapartum, and via breastmilk) to HIV; and (ii) variation in ma ternal infectivity. The model was estimated from different sources of epidemiological data: a retrospective cohort study of children born to HIV-1-infected women in Sao Paulo State, Brazil, the International Re gistry of HIV Exposed Twins, and the AIDS Clinical Trials Group 076 tr ial, which assessed the effectiveness of zidovudine in preventing moth er-to-child HIV transmission. Results: Variation in maternal infectivi ty results in higher average risk of breastfeeding-related transmissio n in the early stages of breastfeeding than in the late stages, even i n the absence of a direct relationship between transmission risk and t he age of the child. However, the available data were unable to resolv e the quantitative importance of this mechanism. Conclusions: Our mode l has helped identify a previously unrecognized determinant of the tim ing of breastfeeding-related HIV transmission, which may have adverse implications for the effectiveness oi certain interventions to reduce mother-to-child HIV transmission such as maternal antiretroviral thera py in breastfeeding populations and the early cessation of breastfeedi ng. (C) 1998 Lippincott Williams & Wilkins