It is possible that one or more genetic factors may be involved in an individual's susceptibility to migraine, for some women seem predisposed to it. Compared to normal individuals, the blood vessels of migrainous patients are less sensitive to the effect of cooling, and their platelet membranes retain serotonin less efficiently. This observation substantiates a current theory that migraine headache is triggered by a rapid drop in blood serotonin. Serotonin is a chemical substance primarily present in the platelets. It constricts blood vessels and is thought to be involved in the mechanism of migraine.
Pregnancy also influences migraine.
In female patients with migraine, some women find their attacks disappear completely, occur less often or are milder during pregnancy. Attacks either worsen or remain unchanged in others. Oral contraceptives may affect the incidence of migraine. This was more common a decade or more ago because of the dose of higher estrogen content pills. Some of the newer cyclical pills may also exacerbate migraine.