Co-creation of a citizen-science research initiative with a collaborative team of community members and university-based scientists to address regional disparities in maternal and fetal health outcomes for Black birthing people. Citizen scientist-led projects, where community members actively contribute to each discovery step, from setting a research agenda to collecting data and disseminating results, can extend community participatory research initiatives and help reconceptualize traditional research processes. The Pregnancy Collaborative is a citizen-science research initiative and one of nine scientific committees of The Pittsburgh Study-a longitudinal, community-partnered study designed to bring together collaborators to improve child thriving. Ten community members and five university-based scientists participated during all phases of developing a citizen-scientist collaboration over an initial two-and-a-half-year period. Phases include forming the Pregnancy Collaborative and group research ethics training; co-creating a research agenda grounded in shared principles; and community-partnered data collection, analysis, and dissemination. These phases produced three key co-designed products: (1) a mission and vision statement of the Pregnancy Collaborative, (2) a Collaborative-endorsed research agenda, and (3) a citizen-scientist-executed research survey. Lessons learned from the formation of the Pregnancy Collaborative highlight the importance of equitable power distribution through bidirectional knowledge sharing and by centering intellectual effort, lived experience, and tools and resources of those affected by health inequities. Using a citizen science approach to co-designing and executing research helps us move maternal health inequity work from "research on" to "research with."