question.

[somastar.livejournal.com]

i have researched a lot of topics somehow related to menstruation--endometriosis, bleeding during pregnancy, etc. at some point or another, i read about something that has a very strange symptom--periods with blood that is dark, dark red, like brown, and blood that is bright bright red, almost pink. like, absolutely no in between. i cannot remember what it is, and though this seems kind of normal to me, it's got me wondering what it could have been that i read about. any ideas? anyone know of anything that causes these two polarities so happen? thanks.