The California Abundant Birth Project (CA-ABP) is a guaranteed income program for pregnant people at greatest risk of birth inequities in five California counties (San Francisco, Alameda, Contra Costa, Riverside, and Los Angeles), funded by the State of California, municipal governments, and philanthropic funding. The California Abundant Birth Project will provide unconditional, monthly income supplements during pregnancy and postpartum to randomly selected participants, with the goal of curbing financial stress and promoting healthy pregnancy outcomes. The goal of this project is to evaluate the impact of this guaranteed income program on birthing outcomes, maternal and child health, and children’s early outcomes.