Yes, it's indeed a very weird question and "possibly" there is more reasons for the worry than just the appearance of pregnancy.
As a commoner, I can know of sure if a woman is pregnant after her 6th month onwards just from her physical appearance with my eyes doing the scanning job. As for scanners at the airports, they do not look for shapes of the human anatomy, male or female. I guess that part is done visually by the trained and vigilant staff present. The scanners scan for metallic objects that may be hidden on the body which could be a threat to the aircraft, the crew and the passengers.