Alcohol, Cigarette, and Cannabis Use Between 2002 and 2016 in Pregnant Women From a Nationally Representative Sample

had an increased risk of venous thromboembolism, infection, blood transfusion, and maternal mortality. The mechanisms through which obesity increases risk for CD are poorly understood. This study presented a conceptual framework that hypothesized how obesity may impact factors that would lead to a CD. Obesity has been found to be associated with elevated risk of CD in various populations and environments. Even when comorbidities are adjusted for, this association continues. For nulliparous patients, three main proximal mediating mechanisms include (1) increased incidence of obstetric complications and maternal comorbidities, (2) delayed onset of labor, and (3) longer duration of labor. In patients with a prior delivery, the history of prior CD increased the risk of CD in subsequent deliveries. Distal mediators of risk for CD include induction of labor or planned prelabor CD. Obesity could moderate the likelihood of CD by interactions with clinicianlevel or hospital-level factors. In addition, obesity may increase the acuity of chronic diseases or obstetric complications. The association between obese parturients and their increased risk of CD is complex and it is difficult to separate the effect obesity can have on multiple contributors to CD risk. It is recommended that future studies should assess the validity of the proposed framework and seek to understand the contributions of each potential pathway between obesity and CD. Evidence-based recommendations are needed to reduce preventable CD in obese parturients, and modifiable mediators and moderators of the relationship between obesity and increased risk of CD should be targeted.