LAUSR

pregnant women,1,2,4 we found an elevated risk of stroke among women with migraines. Approximately one-fourth of the excess cases of maternal stroke associated with migraine were attributable to hypertensive disorders. This suggests that other pathways exist between migraine and stroke during the perinatal period, potentially through pathophysiologic changes, such as increased blood volume and cerebral circulation.2 The limitations of this study include the uncertain temporality of migraine, hypertension, and stroke in prenatal models. As severe headache can accompany strokes or preeclampsia, migraine may be coded as a sequela of either condition, the timing of which would not be distinguishable on discharge summaries. Mediation assumes that the exposure (migraine) causes the mediator (hypertension), which in turn causes the outcome, and deviations to this temporal sequence or framework would affect findings and interpretation. Also, it is likely that only severe and active migraines are recorded in discharge summaries, which could lead to stronger risk ratios that are not generalizable to less severe migraines. Finally, we did not have any data on treatment of migraine and all models are vulnerable to unmeasured confounding. In conclusion, approximately 25% of the excess risk of maternal stroke associated with migraine was mediated through hypertensive disorders. Although strokes are rare events, the associated morbidity and mortality warrants focus on identifying modifiable intervention targets.