I'd go and get it checked out... bizarre the midwives dismissed it so easily!!???
I guess it could be totally normal, I havent been thru the later stages yet but perhaps it could also be a varicose vein or a prolapse or something.. or maybe you arejust swollen with all the extra fluid, but i think a quick check by your care provider would at least put your mind at ease... you poor thing!! gosh being preg just starts all sorts of things hey!!!