Answer:
1.Most movies only take a few months at most to film, although there are exceptions. If an actress got pregnant at the beginning of fiming, then she would not really show overt signs of pregnancy during the film shooting. If it was a longer production such as a TV series, a professional actress would inform the producers as soon as she was sure that she was pregnant, and they would plan accordingly. One obvious option would be to shoot distance scenes early in the pregnancy, and shoot close-up scenes later on.