Is your profession a roadblock in your pregnancy?

Hi, I was wondering if being pregnant may be a condition that is difficult to coordinate with your job. For instance, a researcher in a chemistry laboratory, a hairdresser, a policeman, ... I wonder how women with these or other occupation deal with the fact of being pregnant, as well as, how the firm / company, supports or not this process.
I work as a consultant so there's not big deal aside from the fact of feeling sleepy at times but there are many other jobs where the challenges are others. 
Thanks for sharing your stories in advance