I agree with all of these ladies- and don't be afraid to get your OB behind you- mine was happy to write notes for work or whatever I needed to decrease my stress and help my health (severe m/s). I am struggling with it again this time (twins) and am now at a different job. I've been here 3 years (my son is 5), so I've put some time in, but we are short staffed as well. My boss and department head both know I am preggo, although it is early (8weeks) just due to the fact that I am fighting such bad nausea. I've worked from home one day last week and have really fought to make it in this week. I've made it, but took a long lunch at home today laying on the couch. I might be talking to the OB next week on considering some options on working from home. My office doesn't do that as a normal thing though- so very nervous about it!
But do what you have to for your health and the baby! and get your OB's support and help if you need her back up to tell them you can only work a certain amount of hours or whatever it might be.