Migraine headaches are due to genes that make the brain more susceptible to changes. For example, both weather changes and variation in hormone levels can lead to a migraine attack. 

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Throughout their lifetime, people born with the female sex naturally go through lots of fluctuations of hormone levels, such as estrogen, which affects migraine. (There is currently not much data available on migraine in transgender women and transgender men. Transgender women receiving estrogen tend to have a worsening in headaches. Headaches tend to affect transgender women at similar rates as cisgender women. Transgender men receiving testosterone tend to have an improvement in headaches.  This is thought to be due to suppression of estrogen fluctuation.)

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The relationship between the levels of sex hormones, such as estrogen and progesterone, and migraine is complicated and not fully understood. Our current understanding is that variations in hormone levels trigger migraine attacks in those susceptible to migraine. The natural changes in the levels of sex hormones throughout women’s lives tend to correlate with changes in migraine attacks. 

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• Women start to be more affected by migraine than men around puberty when they start menstruating.
• Once hormone levels stabilize in the second and third trimester of pregnancy, the great majority of women see an improvement in their migraine attacks.
• Often, migraine attacks tend to come back to their pre-pregnancy frequency and severity after delivery. More than one third of women have migraine attacks again within one week from delivery. Nearly two third have migraine attacks within one month from delivery. 
• Breastfeeding prevents some of the hormonal fluctuations after delivery and hence delays the recurrence of migraine post-delivery.  
• The menopausal transition is a very long process that takes 10 years on average and occurs in several phases. There is a lot of variation in the levels of sex hormones during the transition to menopause, which might change the frequency and severity of migraine attacks during that time - sometimes for better, sometimes for worse.  
• Postmenopausally, most women experience a significant improvement in the frequency of migraine, especially painful migraine attacks.  Some women who experience aura with their migraines report continuing to experience aura (especially visual symptoms) even with fewer painful attacks.

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In addition to the natural variation in sex hormone levels throughout women’s lives, women might have fluctuations in hormone levels due to medications such as birth control medications or infertility treatments. As with natural variations in sex hormone levels, variations induced by medications can also lead to migraine attacks. 

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Of note, migraine does not cause infertility. There are conditions associated with increased risk of infertility like endometriosis that are also associated with a higher chance of having migraine. Some infertility medications can trigger migraine attacks, and many fertility specialists will work with your headache specialist to come up with a good plan if this occurs. Although most medications used for migraine do not cause infertility, Depakote (valproic acid) is usually avoided in women of reproductive age or at least used in the lowest possible dose, as it can lead to polycystic ovary syndrome, which might lead to fertility issues.

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In summary, any biological event or medication that causes fluctuations in hormonal levels can lead to more migraine attacks. Examples include menstruation, post-partum period, post-breastfeeding period, menopausal transition, birth control or infertility medications. Menses, conception planning, pregnancy, and breastfeeding all have implications for the treatment of migraine. 

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