Objective: Hypertensive disorders of pregnancy are leading causes of morbidity and mortality in all pregnancies in the United States. The objective of this dissertation was to examine the impact of risk factors, including the use of antidepressants (chapter 1), folicacid containing supplements (chapter 2), and cigarettes (chapter 3), on the development of gestational hypertension and preeclampsia. Methods: Data was collected from pregnant women who participated in the MotherToBaby cohort studies from 2004 to 2014. Maternal information was collected at intake, every three months until the birth of the baby and once after birth. Data collected at these interviews included demographics, medical history, lifestyle factors, substance use, medication use, fetal sex, and study outcomes. Unadjusted and adjusted odds ratios (OR) and their 95% confidence intervals (CI) were generated using logistic regression to assess the association between the risk factors and the outcomes. Results: A total of 3,474 women were included in the study. In chapter 1, women who continued to use antidepressants after 20 weeks of gestation were at higher risk for gestational hypertension (aOR: 1.83; 95% CI: 1.05, 3.21) after adjustment. Women who used serotonin-norepinephrine reuptake inhibitors were at significantly increased risk for gestational hypertension, but not preeclampsia. Findings from chapter 2 indicated no significant association between folic acid-containing supplement use and hypertensive disorders of pregnancy. Interestingly in chapter 3, smokers had decreased risk (aOR: 0.41; 95% CI: 0.21, 0.79) for gestational hypertension after adjustment. No significant association was observed between smoking and preeclampsia. After stratifying by timing of supplements use, smokers who used folic-acid containing supplements after recognition of pregnancy were at an even more decreased risk for gestational hypertension (aOR: 031; 95% CI: 0.13, 0.75). Conclusion: Hypertensive disorders of pregnancy are poorly understood and remain major causes of maternal morbidity and mortality worldwide. Identifying risk factors for these disorders is important in planning intervention strategies. Additionally, further research is needed to examine the biological mechanisms by which risk factors contribute to the development of these disorders.