PROJECT SUMMARY Maternal cannabis use among pregnant women has doubled over the last few years in the United States (US). Medical and recreational cannabis use is now legal in many states across the nation which has influenced an increase in cannabis use prevalence. Legal expansion might alter cannabis risk perceptions, leading to the potential misguided belief that cannabis is a relatively safe substance. The antiemetic effects of cannabis have been well-established for decades. Because cannabis is used to alleviate nausea and vomiting in cancer patients, it might be thought that cannabis can treat morning sickness. Morning sickness is pregnancy-related nausea and vomiting, and can sometimes be severe (i.e., Hyperemesis gravidarum); it is common among pregnant women in their first trimester of pregnancy. Little is known about the relationship between morning sickness and cannabis use. I propose to estimate the odds of maternal cannabis use given the severity of morning sickness experienced during pregnancy, trimester-by-trimester. Current literature indicates a lack of clear evidence establishing causality between maternal cannabis use and adverse short-term birth outcomes. Studying outcomes such as low birth weight, preterm, birth, small-for- gestational age, Apgar score, neonatal intensive care unit (NICU) admission is important given the potential for long-term effects that result from these infant morbidities. Prior studies lack reproducibility, possibly due to methodological issues such as the use of retrospective study designs. As Michigan became the first state in the Midwest to legalize the recreational use of cannabis by adults at least 21 years of age in 2018, it is imperative to investigate the effects of prenatal cannabis use using a prospective cohort study design. This dissertation proposal aims to estimate the suspected causal link between cannabis use during pregnancy, morning sickness, and a set of birth outcomes (e.g., birth weight, gestational age, preterm birth, Apgar score at birth, and NICU admission following birth) across pregnancy trimesters using data for the Michigan Archive for Research on Child Health (MARCH) study. The support of the NIDA R36 dissertation award will launch me into the role of an independent researcher, and will strengthen my ability to extend this work as an early stage investigator in academia.