Estimates are based primarily on case-control studies and a smaller number of cohort studies primarily from northern European countries, which limits generalizability to other populations. Further research is needed to better understand the subgroups of women who may be at risk for hemorrhagic stroke associ- ated with OCs based on age, race/ethnicity, genetic makeup, and parity. In addition, research assessing the value of specific biomarkers of endothelial function, such as von Willebrand Bushnell et al Guidelines for Prevention of Stroke in Women 1561 factor and ADAMTS13, before and during OC use, as well as after an arterial thrombotic event, is warranted. OCs: Recommendations 1. OCs may be harmful in women with additional risk factors (eg, cigarette smoking, prior thromboembolic events) (Class III; Level of Evidence B).224,225 2. Among OC users, aggressive therapy of stroke risk factors may be reasonable (Class IIb; Level of 3. Routine screening for prothrombotic mutations before initiation of hormonal contraception is not useful (Class III; Level of Evidence A).229 4. Measurement of BP before initiation of hormonal contraception is recommended (Class I; Level of Menopause and Postmenopausal HT Menopause Onset Exposure to endogenous estrogen has been hypothesized to be protective for stroke in premenopausal women; however, given logistical difficulties in collecting longitudinal data on endogenous hormones and the large sample sizes that would be required to study stroke in younger women, no study has investigated the relationship between endogenous hor- mones and stroke as women transition through menopause. 