OBJECTIVES: To estimate the association between HIV disease progression and the incidence of recognized pregnancy; to estimate the risk of subsequent fetal loss. METHODS: A total of 191 women (92 HIV seropositive and 99 HIV seronegative at enrolment) aged 15-49 years in an HIV clinical cohort were invited to attend routine clinic visits every 3 months. Information on HIV progression collected at the visit was related to whether there was a pregnancy beginning in the following 3 months. Visits were excluded where the woman was already pregnant, lactating, using modern contraceptives or if there was inadequate follow-up. RESULTS: There were 2524 eligible visits and 216 recognized pregnancies. The reported frequency of sexual intercourse diminished with advancing HIV disease. The adjusted odds ratio (OR) for pregnancy when the woman was in WHO stage 1 compared with HIV seronegatives was 0.58 [95% confidence interval (CI), 0.36-0.93]; stage 2, 0.47 (95% CI, 0.25-0.91); stage 3, 0.43 (95% CI, 0.25-0.74); and stage 4, (AIDS) 0.14 (95% CI, 0.02-1.09). The findings were similar for CD4 cell count, time from seroconversion and time before AIDS. There was an increase in fetal loss from the early stages of HIV infection (adjusted OR for stage 1, 5.38; 95% CI, 1.57-18.44), there were very few recognized pregnancies in the advanced stages. CONCLUSIONS: Fertility is reduced from the earliest asymptomatic stage of HIV infection resulting from both a reduced incidence of recognized pregnancy and increased fetal loss. The greatest reduction in fertility was observed following progression to AIDS when there was a very low incidence of recognized pregnancies.