answer:It happened to me once. I just told them I wasn’t and said I always hold a lot of my weight in my stomach. Of course they apologized, and I told them not to worry about it. It was during a time that I had had a few miscarriages, so the people around me knew I was trying. If I know the woman I usually only ask a woman based on her breasts getting huge, not looking a little overweight, and I have always been right. Of course if she is far along and generally was thin it gets pretty obvious if she has a preggers belly. If I don’t know the woman the only time I might acknowledge her pregnancy is to let her take my seat, or step ahead of me in the bathroom line if she looks uncomfortable.