I think there is a federal law that states that unless the job involves something hazardous to either/or/both the mother and the fetus, the company CANNOT fire you for being pregnant. First, they have to locate a job within the company that isn't hazardous. If the employer can't, then s/he has to place the expectant mother on maternity leave or something like that until she is out of the hospital.
Perhaps Nanaea or Barb can look it up on the internet to doublecheck my facts (I hope you don't mind me "volunteering" you for this, Nan & Barb :).).