Typically, are pregnant women and other family caregivers as productive as other employees?

They can be. Depends on the person and their health and their job and their pregnancy situation. When I was a resident in training many moons ago, my chief resident who was 3 years ahead of me and the first female in the program, worked right up until she went into labor, in fact she was in the middle of doing a hysterectomy when her water broke, she finished the case and then went up to the labor room.