Cannabis use in pregnancy is becoming increasingly common despite recommendations from healthcare providers and professional organizations for abstinence. Evidence exists that cannabis exposure in utero, particularly after the first trimester, is associated with risks of adverse pregnancy outcomes and negative effects on the long-term neurodevelopment of the exposed neonate. Despite this, approximately one in four pregnant women who uses cannabis will continue to use throughout her pregnancy. The data that exist currently suggest that continued use in pregnancy is associated with the highest risk of adverse outcomes. However, most of our understanding of patterns of use come from cross-sectional surveys and consist only of the binary outcomes of continuation or abstinence. There is a need for longitudinal data evaluating trajectories of cannabis use during pregnancy, including changes such as decreases in use. Defining these trajectories will help to further delineate if a dose-dependent relationship between exposure and outcomes exist. Equally as important, understanding both baseline and time-varying factors that are associated with different cannabis use trajectories can be used to inform counseling, support and treatment efforts with the ultimate goal of improving maternal and child health. We plan to recruit 1,200 pregnant people who present for prenatal care at six different clinical sites across two institutions in Maryland and California. The cohort will include 800 people who self-report cannabis use within the 30 days prior to pregnancy recognition and 400 who do not. We will collect baseline demographic information, health and mental health history and detailed information on frequency, quantity and mode of cannabis use and other substances prior to and since recognition of pregnancy. We will then follow these women throughout pregnancy with monthly, electronic surveys using Timeline Followback to quantify use. In addition to self-report of use, we will use urine drug testing for confirmation. Latent Variable Mixture Modeling will be used to define varying trajectories of cannabis use in pregnancy. In order to evaluate both baseline and time-varying factors associated with differing trajectories of use, we will also capture data on mental health status, pregnancy symptoms, motivations and intentions for use and social determinants of health at enrollment and once per trimester throughout pregnancy. We will compare birth outcomes between different cannabis use trajectories and those of women who do not use. We intend to 1) define trajectories of cannabis use during pregnancy among women who used cannabis within the month prior to pregnancy recognition 2) determine both baseline and time-varying factors associated with different cannabis use trajectories 3) compare birth outcomes across cannabis use trajectories to those of pregnant people who do not use cannabis. The results of this study will aid in the development of more comprehensiv...