I have worked with several mothers who had migraines while
breastfeeding, while they do seem to be in some way hormone related,
they also seem to be related to hydration. Something happens with
anti-diuretic hormones during let-down and this can influence
capillary response.  Anyway, having a glass of water before nursing
and drinking enough to have light colored urine seems to help
decrease the incidence and severity of migraines in some women. Has
anyone else had experience with this?