OBJECTIVE: To study the prognostic role of pregnancy on the progression of human immunodeficiency virus (HIV) infection. METHODS: In a prospective cohort study at the Bordeaux University Hospital, France, 57 women who completed a pregnancy during the course of their HIV infection were compared with 114 HIV-infected women who never conceived. The two groups were matched on CD4 lymphocyte count (CD4), age, and year of HIV diagnosis. The main outcome measures were death, occurrence of a first AIDS-defining event, and drop of the CD4 below 200/mm3. RESULTS: The mean follow-up period in pregnant women was 61 months from HIV diagnosis (median CD4 at entry 455/mm3) and 54 months from beginning of pregnancy. Nonpregnant women were followed-up for 50 months since HIV diagnosis (median CD4 460/mm3). The proportion of asymptomatic women at entry in the study was 51 of 57 (90%) in pregnant and 87 of 114 (76%) in nonpregnant women. No significant difference was observed between the two groups with regard to the different end points studied, even after adjustment for other prognostic variables. Adjusted hazard ratios (pregnant/nonpregnant) were 0.92 for death (95% confidence interval [CI] 0.40-2.12), 1.02 for occurrence of a first AIDS-defining event (95% CI 0.48-2.18), and 1.20 for drop of the CD4 to less than 200/mm3 (95% CI 0.63-2.27). CONCLUSION: In a cohort of HIV-infected women with mild to moderate immunosuppression, pregnancy did not accelerate progression to AIDS or death.