The U.S. Centers for Disease Control and Prevention (CDC) developed and implemented the CDC COVID-19 Vaccine Pregnancy Registry (C19VPR) to monitor vaccine safety. Potential participants who received a COVID-19 vaccine in pregnancy or up to 30 days prior to their pregnancy-associated last menstrual period were eligible to participate in the registry, which monitored health outcomes of participants and their infants through phone interviews and review of available medical records. Data for select outcomes, including birth defects, were reviewed by clinicians. In certain cases, medical records were used to confirm and add detail to participant-reported health conditions. This paper serves as a description of CDC C19VPR protocol. We describe the development and implementation for each data collection aspect of the registry (i.e., participant phone interviews, clinical review, and medical record abstraction), data management, and strengths and limitations. We also describe the demographics and vaccinations received among eligible and enrolled participants. There were 123,609 potential participants 18-54 years of age identified from January 2021 through mid-June 2021; 23,339 were eligible and enrolled into the registry. Among these, 85.3 % consented to medical record review for themselves and/or their infants. Participants were majority non-Hispanic White (79.1 %), residents of urban areas (93.3 %), and 48.3 % were between 30 and 34 years of age. Most participants completed the primary series of vaccination by the end of pregnancy (89.7 %). Many participants were healthcare personnel (44.8 %), possibly due to the phased roll-out of the vaccination program. The registry continues to provide important information about the safety of COVID-19 vaccination among pregnant people, a population with higher risk of poor outcomes from COVID-19 who were not included in pre-authorization clinical trials. Lessons learned from the registry may guide development and implementation of future vaccine safety monitoring efforts for pregnant people and their infants.