The fertility, maternal health, and infant health consequences of reproductive policy change - PROJECT SUMMARY Recent state-level policy changes related to reproductive and pregnancy health have potential impacts on fertility and perinatal outcomes in the United States. Groups with higher baseline rates of pregnancy-related risks—including late entry into prenatal care, preterm birth, low birthweight, and severe maternal morbidity—may be particularly impacted. Additionally, shifts in clinical practices, reduced access to timely maternal care, and increases in stress may contribute to adverse outcomes. The proposed research will estimate the impact of recent reproductive and pregnancy health policy changes on fertility, maternal health, and infant health outcomes over time and across subgroups. We will use high-quality, state-specific monthly data from 2016 through 2024 from several sources, including state birth certificate data compiled nationally by the CDC, Census Bureau data, and administrative hospitalization data from State Inpatient Databases. For each Aim, we will apply a comparative interrupted time series design with control locations to strengthen causal inference while accounting for underlying trends (e.g., declining fertility) and perturbations (e.g., the COVID-19 pandemic). For Aims 2 and 3, we will use a difference-in-differences decomposition approach to quantify how much of the observed change in outcomes are attributable to shifts in the composition of the birthing population versus changes in underlying risks. We propose the following specific aims: 1) Evaluate the impact of recent policy changes on fertility; 2) Determine the impact of these policy changes on severe maternal morbidity; 3) Assess the impact of these policy changes on infant birth outcomes, including preterm birth, low birthweight, and small for gestational age. This work will address important gaps in knowledge regarding the causal impact of policy changes on population health and will generate time-sensitive findings to inform future policies.