About 60% of women who have migraine experience attacks before or during their menstrual period, although only about 10% to 15% will have migraine only when they have their menstrual period. The majority of women will have migraine at other times of their cycle but will experience attacks of greater severity one to two days before or during their menstrual period. The timing of many menstrual-related migraine attacks can be predicted since the greatest vulnerability for attacks occurs between two days before and three days after the start of menstrual flow. This predictability allows women to use short-term preventive treatments that are aimed at stopping migraine attacks before they occur or reducing the intensity of headaches that might still occur.
Menstrual headaches appear to occur when estrogen levels in the blood drop during the menstrual cycle. Estrogen is involved in setting the threshold for pain activity. Falling estrogen levels are associated with a greater sensitivity to pain and increased activity in body systems that cause inflammation. These changes can make women more susceptible to experiencing several different types of pain, such as headache, cramps, and muscle or joint aches, just before or during their menstrual period. Taking oral contraceptive pills (i.e., birth control pills) can exaggerate the drop in estrogen levels before the start of menstrual bleeding. Consequently, taking the pill can sometimes worsen migraine patterns. Many women will experience an improvement in their migraine after menopause.