More than half of migraines in women occur right before, during, or after a woman has her period. This often is called "menstrual migraine." But, just a small fraction of women who have migraine around their period only have migraine at this time. Most have migraine headaches at other times of the month as well.
How the menstrual cycle and migraine are linked is still unclear. We know that just before the cycle begins, levels of the female hormones, estrogen and progesterone, go down sharply. This drop in hormones may trigger a migraine, because estrogen controls chemicals in the brain that affect a woman's pain sensation.
Talk with your doctor if you think you have menstrual migraine. You may find that medicines, making lifestyle changes, and home treatment methods can prevent or reduce the pain.
This answer is based on the source infromation from the National Women's Health Information Center.