ABSTRACT: Background: The safety of birth center care for low-risk women is an important issue, but it has not yet been studied in randomized controlled trials. Our purpose was to evaluate the effect of birth center care on women's health during pregnancy, birth, and 2 months postpartum by comparing the outcomes with those of women experiencing standard maternity care in the greater Stockholm area. Methods: Of 1860 women, 928 were randomly allocated to birth center care and 932 to standard antenatal, intrapartum, and postpartum care. Information about medical procedures and health outcomes was collected from clinical records, and a questionnaire was mailed to women 2 months after the birth. Analysis was by “intention to treat;” that is, all antenatal, intrapartum, and postpartum transfers were included in the birth center group. Results: During pregnancy, birth center women made fewer visits to midwives and doctors, experienced fewer tests, and reported fewer health problems. No statistical difference occurred in hospital admissions (4.8%) compared with the control group (4.7%). During labor, birth center women used more alternative birth positions, had longer labors, and did not differ inperineal lacerations. In both groups 1.7 percent of women developed complications, requiring more than 7 days of hospital care after the birth. During the first 2 postpartum months, about 20 percent of women in both groups saw a doctor for similar types of health problems, and no statistical difference occurred in hospital readmissions, 1.4 and 0.8 percent in the birth center and control groups, respectively, Conclusion: The results suggest that birth center care is effective in identifying signijicant maternal complications and as safe for women as standard maternity care.