<qa>  What is the term for a migraine?Subjects who have experienced regular menstrual cycles for the past 6 months every 21 to 35 days Subjects who have a history of migraine with or without aura that meets IHS criteria for at least 6 months preceding the study. Subjects who have headaches associated with menstruation, either pre-menstrually or menstrually defined as from day -3 through the cessation of menstrual flow at least 75 of the time 3 out of the past 4 months. Subjects must experience a menstrually-associated migraine during the baseline month, as defined above. Subjects must be able to accurately predict onset on menses within 2 days. This will be confirmed during the baseline month. Subjects who have been on stable headache preventive medications for the 3 months prior to screening. Subject has negative urine pregnancy test prior to study entry, and is using or agrees to use for the duration of participation a medically acceptable form of contraception as determined by investigator, if female of child-bearing potential Subject is able to understand and comply with all study requirements Subject provides written informed consent prior to any screening procedures being conducted 