Blood clots can be fatal if they break off and travel to the heart or lungs.
Researchers do not yet know why migraine sufferers appear to be more prone to clots.
This study is in the journal Neurology.
Fatal blood clots linked to migraines
Researchers in Italy took ultrasound images of necks and thighs in older adults.
Of those who to get migraines, 19 percent had one or more leg clot, but only 8 percent of those who did not get migraines had leg clots.
