I think it can be pretty judgmental to say that some pregnant women are using their pregnancy as an excuse to not exercise while in fact not knowing the details of a specific person. I am very certain that it's common, but I also know a few women who were quite incapacitated at some point of their pregnancy and in particular had a really hard time walking. Just because one woman's pregnancy was smooth until the end doesn't mean it's the same for everyone. I don't see pregnancy as a disease or anything, but it's also not quite business as usual for a lot of people.

Case in point, I was at a talk by Mia Birk last week. Mia Birk, the bike activist and planner who wrote the book Joyride, is the pretty amazing woman who conducted most of the transformation of Portland into a cycling-friendly city. In the Q&A period, someone asked her about common interests (from a political point of view) between people with disabilities and cyclists when it comes to public transportation infrastructure. In her response, she mentioned that in the last month of one of her pregnancies she was very, very miserable, had a really hard time walking, and all of a sudden totally understood why bus stops were located every other block, not every 4th block. You can hardly accuse Mia Birk of making excuses not to exercise, but I'm pretty sure that she would gladly have been dropped off at the door of any store rather than walk from the confines of the parking lot (dodging crazy parking-spot seekers in the process) during that miserable month.