Generally the menstrual cycle stops sometime in a woman's mid fifties, but can begin to come irregularly as early as the early to mid forties. Granted, this isn't true for everone. It can still be totally normal to go through menopause and be done with it in your forties. As for knowing when the last one will come, I don't know if that is something you can tell until you stop having them and notice it's absence. Usually they will start coming sporadically. You may go three months without having one and then get one in the fourth month. Then have another one after only two weeks, followed by another three month dry spell. So you have to go several months in a row to know for sure. I believe that is also a test your doctor can perform to tell what stage you are in.
at 12:33 AM on Jun. 2, 2009