The aim of this study was to estimate the prevalence and correlates of suicidal ideation among low-income pregnant women living in Brazil. We performed a cross-sectional analysis of 831 women surveyed during 20 to 30 weeks of pregnancy using the Self-Report Questionnaire-20. The prevalence of suicidal ideation was 6.3%. The factors associated with suicidal ideation were common mental disorders, single partner status, past psychiatric history, and smoking tobacco. All cases of suicidal ideation were associated with common mental disorders.