OBJECTIVE: To determine the role of HIV-1 infection on miscarriage, we compared the obstetric histories of a cohort of HIV-1-infected and uninfected Italian women. DESIGN: Retrospective study. METHODS: The study participants were women (with at least one reproductive event) with HIV-1 infection or HIV-1-negative sharing the same exposure modalities; all women were attending a network of 16 infectious disease units in 12 Italian cities. Trained interviewers used a standard questionnaire to collect information on obstetric history [i.e., number of pregnancies, pregnancy outcome (live birth, spontaneous or induced abortion) and time of occurrence of these events (i.e., year of birth)]. The association between spontaneous abortion and HIV-1 status at the time of pregnancy was evaluated. RESULTS: The analysis included 272 women and accounted for 480 pregnancies (217 in HIV-infected women, 132 in uninfected women and 131 in women with undefined HIV status) and 60 miscarriages (23 in HIV-infected women, 22 in uninfected women and 15 in women with undefined HIV status). We estimated an adjusted odds ratio of 1.67 between spontaneous abortion and HIV-1 infection. CONCLUSIONS: We observed a 67% increase in risk of spontaneous abortion among HIV-1-infected women compared with HIV-1-negative women. This result should be considered in the counselling and management of women with HIV-1 infection who are of reproductive age.