I have chronic migraines, so I get migraines all the time, but...!
I always get lots of migraines before my period. And, when my chronic migraines are in remission or under control, I still get menstrual migraines... so, no matter what, I will always get at least one migraine before my period!
I think the number of migraines I have stays pretty consistent, even with menstruation. I have chronic migraines, too. I have other headaches involved as well.
The thing I find best for the prevention of menstrual migraines is Magnesium citrate @ 400mg a day because I find that not only does it help to prevent migraines, but I find that it also helps to prevent my menstrual cramps too.
There is a triptan that is specifically for Menstrual Migraines that is called Frovatriptan (brand name is Frova). If anyone who suffers from Menstrual Migraines finds that their current triptan just isn't doing the job... especially if their menstrual migraines come back later after they use their regular triptan... then they should ask their doctors about Frovatriptan because it is supposed to work much better for Menstrual Migraines than any of the other triptans. One of the reasons why is because it has an especially long half life, so it stays in your system longer than any of the other triptans, so your migraine probably won't come back after using just one triptan... and apparently with menstrual migraines, many women find that their migraines tend to come back after using just one regular triptan, so that's why this type of migraine and Frovatriptan is such a good fit. Anyway, ask your doctors about it if you have menstrual migraines and if you are unsatisfied with your current acute treatment plan.
I think it is quite common for female migraine sufferers to experience it before and at the beginning of the migraine. I believe your estrogen drops to it lowest point and your seratonin level I think drops too at the start of a mense. I used to suffer my worst migraines with my menses. I heard there was hope with menopause shortly after my migraines became chronic, that the migraines might go away. I know of someone that became true for. But not me with my surgical menopause. I don't take any HRT, but I have a lot of issues that contribute to causing migraines, including severe TMJ dysfunction (have osteoarthritis in jaws).