<qa>  What is the estimated start of the menstrual bleeding?Comparison: In a double-blind, randomized cross-over trial women with strictly defined menstrual migraine will receive treatment with 100 microg 17-beta estradiolplacebo transdermally one week before the estimated start of the menstrual bleeding and twoo weeks on. After three cycles and a wash-out period the treatment will be repeated but now with the tratment the woman did not have during the first treatment period. The women serve as their own controls. 