MEASURING THE IMPACT OF HIV ON FERTILITY IN AFRICA

Objectives: To review evidence for the impact of HIV on fertility from empirical sources pertaining to African populations and to discuss th e implications for surveillance based on antenatal clinic populations. Methods: The theoretical equivalence between the fertility rate ratio for HIV-positive to HIV-negative women and the relative odds of being infected for pregnant women compared with the general female populati on is demonstrated. This equivalence is used to compare fertility diff erentials measured in cohort studies with those calculated indirectly from antenatal clinic data. Data from case-control studies and theoret ical predictions from a model of the proximate determinants of fertili ty and HIV incidence are used to obtain plausible explanations of the fertility differences. Estimates of population attributable change are made. Results: Fertility of HIV-positive women is lower than that of HIV-negative women, in all but the youngest age-group, and the differe ntial increases with women's age and epidemic duration. Selection for early start of sexual activity explains the reverse pattern at younger ages. Lower fertility amongst HIV-positive women causes a population attributable decline in total fertility of the order of 0.4% for each percentage point HIV prevalence in the general female population. Conc lusions: In populations that do not use contraceptives, HIV-positive w omen have lower fertility principally as a result of foetal losses con sequent to infection with HIV and coinfection with other sexually tran smitted diseases; behavioural factors tend to enhance this differentia l. Other factors being equal, HIV prevalence estimates based on antena tal surveillance underestimate true prevalence in women in the childbe aring years. (C) 1998 Lippincott-Raven Publishers.