The post-Dobbs era has seen unprecedented restrictions to abortion care in the United States. As of January 2024, 14 states have completely banned abortion, four ban abortion after early gestations, and others are adjudicating restrictions in the courts. These bans impact abortion access for residents of restrictive states, and for pregnant people nationwide—as the abortion infrastructure in less restrictive environments strains to serve individuals traveling for care. This study captures the impact of state-level bans via an innovative data collection and modelling approach that produces nationally representative, monthly estimates of abortions in the formal health care system in 2023. The Monthly Abortion Provision Study uses a stratified sampling design to survey abortion-providing facilities each month. Facilities are included in one of two sampling arms. The first, surveyed every month, includes independent facilities playing key roles in abortion provision in their states, major virtual-only clinics, and Planned Parenthood affiliates. The second arm consists of facilities drawn randomly from all remaining, known US abortion providers; each month, 100 facilities are sampled with replacement. Facilities in both sampling arms are asked to provide data on caseloads, patient state of residence, and gestational duration, as well as one rotating question that changes monthly based on current policy developments. This analysis combined data from sampled facilities with historical facility-level data in a hierarchical Bayesian time series model to produce nationally representative estimates of abortion counts, gestational duration and travel across state lines in 2023, as well as estimates of change compared to 2020. Findings include nationally representative abortion estimates for 2023, by state, month, and gestational duration, as well as estimates of travel across state lines. As compared to 2020 (the last full year for which comprehensive estimates are available), we found substantial increases in travel across state lines, particularly from states with total abortion bans, driving large increases in abortion caseloads in states bordering those with abortion bans. We also found that abortion counts increased among residents in almost all states where it remained legal. Several states implemented partial abortion bans in 2023; following these policy changes, we found significant and sustained declines in abortion caseloads in these states, largely without commensurate increases in surrounding states. Overall, we found that in 2023, the number of abortions provided in the United States substantially exceeded the number of abortions provided in 2020. Importantly, these findings reflect abortions occurring in the formal US health care system only; they do not include self-managed abortions, and as such cannot be considered a complete count of abortions nationwide. Rapidly changing state-level abortion policies must be met with timely, policy-relevant data on abortion access. The Monthly Abortion Provision Study is the first to estimate abortion in the formal US health care system using nationally representative samples of facilities. Crucially, this strategy potentially lessens the data collection burden on abortion providers, offering a pathway for future work measuring abortion. The findings offer critical new evidence on shifts in abortion provision and patient travel after bans take effect to policymakers, abortion providers and advocates, and the research community. [ABSTRACT FROM AUTHOR]