Do females of non-human races, humanoid or goblinoid, menstruate? They do if they give live birth. Some races are oviparous (egg-layers). Some mothers-to-be of these races, once pregnant, can slow pregnancies (often "drastically") so as to give birth in a warm season, one or even two years hence.#Realmslore
— Ed Greenwood (@TheEdVerse) February 4, 2019
So any race the females of which give birth instead of laying eggs menstruate? Does that include bizarre races like celestials and githzerai? Yes, but not all live-birth races menstruate in precisely the same way as humans (differences in lengths of periods, what’s discharged, and how and when).#Realmslore
— Ed Greenwood (@TheEdVerse) February 24, 2019
Many mammals have estrous cycles, rather than menstrual cycles, and so there are possibilities (even in the non-fantasy world) for something different than menstruation, even among animals that birth live young.