I haven't had a menstrual period since I started working out in February. It was a nice break. But it has hit at last, and hit hard. Bad headache, water retention with all its lovely side effects, fatigue, poor sleep, etc. Ick!
If getting in shape keeps that away for me, it gives me one more incentive. Just as soon as I get over this darn period.
Luckily at my age, when they asked at the hospital "When was your last period?" they didn't insist on a pregnancy test. Unless they did it without asking me. But seriously, at 48? The x-ray guy asked if I wanted one, but I just laughed and said it wouldn't be necessary.
Symbol from http://www.zib.de/Numerik/projects/MenstrualCycle/project.en.html