Background: Cardiovascular disease (CVD) is the leading cause of mortality among US women. CVD risk factors emerge well before onset of clinical disease, requiring a life course approach to prevention. Women of reproductive age are a targeted demographic due to growing burden of CVD risk in this group, and because poor preconception cardiovascular health may cause worse pregnancy outcomes. Few studies have evaluated associations between prospectively measured preconception cardiometabolic risk factors and birth outcomes. Methods: This dissertation includes three studies. Study 1 leverages data from the National Health and Nutrition Examination Surveys administered between 1988 and 2016 to describe trends in the burden of metabolic syndrome-- a clustering of CVD risk factors---among US women ages 18 to 44. Studies 2 and 3 use data from Add Health, a cohort study that recruited and followed US adolescents through adulthood, to evaluate effects of preconception blood pressure (Study 2) and preconception glycemia (Study 3) on two birth outcomes: preterm birth and birthweight. Study 3 additionally examines healthcare and racial and ethnic disparities in preconception hyperglycemia and preterm birth. Results: The prevalence of metabolic syndrome among US women ages 18-44 increased between 1988-94 (14%) and 1999-2004 (21%) and has since plateaued. The prevalence of two metabolic syndrome components, elevated waist circumference and elevated fasting glucose, have increased dramatically with persistent disparities by race/ethnicity (Study 1). Higher preconception blood pressure and higher preconception glycemia were associated with increased risk of preterm birth, even at levels below clinical cutoffs for hypertension and diabetes (Study 2, 3). Women with limited access and utilization of healthcare experienced a disproportionate burden of preconception hyperglycemia and preterm birth (Study 3). Conclusions: The proportion of women entering pregnancy with existing cardiometabolic risk factors like hypertension and diabetes is rising. Interventions to optimize maternal health prior to pregnancy, and to better manage these conditions during pregnancy, could greatly improve health outcomes for women and children.