Hi - I know these machines probably aren't very popular on this forum, but I didn't know where else to ask this question. Does anyone know if it's OK to use those ab roller, "torso track" type machines while pregnant? I'm past my first trimester and don't want to do any improper ab work. I've read guidelines about not doing ab work flat on your back, but never anything about this type of device. Anyone have any pearls of wisdom about this "rolling forward" type of ab workout?