CONTEXT AND OBJECTIVE: Recurrent spontaneous abortion (RSA) is defined as three or more consecutive pregnancy losses before 20 weeks and is associated with several etiological factors related to genetics, anatomy, hormones, infections and immunology, for example. Many cases of RSA remain unclear. New factors or their associations may influence gestational results. The aim was to identify possible single or associated causes of RSA that could predict gestational prognosis for women undergoing investigation and treatment. DESIGN AND SETTING: Case-control study, at the Recurrent Abortion Outpatient Clinic, Department of Obstetrics and Gynecology School of Medicine, Universidade Estadual de Campinas (Unicamp). METHODS: Two hundred and forty-six medical records of women with RSA seen at the Recurrent Abortion Outpatient Clinic, Department of Obstetrics and Gynecology School of Medicine, Universidade Estadual de Campinas (Unicamp), between 1994 and 2003, were evaluated. Data on age, obstetric history, possible etiological factors, treatment and pregnancy outcomes were evaluated. Statistical analysis was performed using odds ratios (OR), logistic regression analysis and decision trees. RESULTS: Two hundred and twenty-nine women were included in the study. The most frequently found etiological factors were immunological, particularly alloimmune factors (93.9%). Women with a single alloimmune factor had better gestational results (77.7% deliveries) than those with other associated factors. Autoimmune factors were associated with a higher abortion rate (OR: 4.30; 95% confidence interval, CI: 1.36-13.63). No association was found between the number of abortions prior to treatment and pregnancy results. Women aged 40 or over presented the highest rate of spontaneous abortion (OR: 5.83; 95% CI: 1.12-30.40). CONCLUSION: Age over 40 years old, immunological factors and two or more concomitant factors were associated with poor gestational outcomes among the women studied.