OBJECTIVE: To characterize the changes in health status experienced by a multi-ethnic cohort of women during and after pregnancy. DESIGN: Observational cohort. SETTING/PARTICIPANTS: Pregnant women from 1 of 6 sites in the San Francisco area (N=1,809). MEASUREMENTS AND MAIN RESULTS: Women who agreed to participate were asked to complete a series of telephone surveys that ascertained health status as well as demographic and medical factors. Substantial changes in health status occurred over the course of pregnancy. For example, physical function declined, from a mean score of 95.2 prior to pregnancy to 58.1 during the third trimester (0-100 scale, where 100 represents better health), and improved during the postpartum period (mean score, 90.7). The prevalence of depressive symptoms rose from 11.7% prior to pregnancy to 25.2% during the third trimester, and then declined to 14.2% during the postpartum period. Insufficient money for food or housing and lack of exercise were associated with poor health status before, during, and after pregnancy. CONCLUSIONS: Women experience substantial changes in health status during and after pregnancy. These data should guide the expectations of women, their health care providers, and public policy.