I get skin tags in my armpits around where my bra underwire ends (pre-pregnancy, haven't worn a wire in a while) - apparently they are caused by friction. You can get rid of them by tying a string around them and that cuts off the blood supply and they die off neatly - some people suggest dental floss. I don't bother, they always come back!

I am glad I found a pregnancy swim suit I like, now no worries about showing my unsightly belly hairs!