Cannabis is the most commonly used illicit substance among pregnant and postpartum women, with the postpartum period being a common time for relapse to cannabis. Currently there are no interventions for preventing return to cannabis use during this vulnerable time. The goal of this research is to better understand risk factors such as stress, craving, anxiety, mood, sleep, and hormone levels that may contribute to return to cannabis use during the postpartum period in order to help develop targeted prevention and treatment interventions in the future.