I also get them more when I'm pregnant, its easy to get run done and your body is under alot of stress when pregnant so use that as a guide to make sure your diet is good and your getting enough rest, mine usually settle after the first trimester for some reason
I typically get less than one per year (one per 2 years?). I've had 2 already and I'm only 24 weeks! I just figured I was being extra-stressy but maybe there's some correlation if it happens to many pregnant women.