OBJECTIVES: To estimate the relationship between HIV natural history and fertility by duration of infection in east and southern Africa before the availability of antiretroviral therapy and assess potential biases in estimates of age-specific subfertility when using retrospective birth histories in cross-sectional studies. DESIGN: Pooled analysis of prospective population-based HIV cohort studies in Masaka (Uganda), Kisesa (Tanzania) and Manicaland (Zimbabwe). METHODS: Women aged 15-49 years who had ever tested for HIV were included. Analyses were censored at antiretroviral treatment roll-out. Fertility rate ratios were calculated to see the relationship of duration of HIV infection on fertility, adjusting for background characteristics. Survivorship and misclassification biases on age-specific subfertility estimates from cross-sectional surveys were estimated by reclassifying person-time from the cohort data to simulate cross-sectional surveys and comparing fertility rate ratios with true cohort results. RESULTS: HIV-negative and HIV-positive women contributed 15 440 births and 86 320 person-years; and 1236 births and 11 240 000 person-years, respectively, to the final dataset. Adjusting for age, study site and calendar year, each additional year since HIV seroconversion was associated with a 0.02 (95% confidence interval 0.01-0.03) relative decrease in fertility for HIV-positive women. Survivorship and misclassification biases in simulated retrospective birth histories resulted in modest underestimates of subfertility by 2-5% for age groups 20-39 years. CONCLUSION: Longer duration of infection is associated with greater relative fertility reduction for HIV-positive women. This should be considered when creating estimates for HIV prevalence among pregnant women and prevention of mother-to-child transmission need over the course of the HIV epidemic and antiretroviral treatment scale up.