Changing jobs and pregnant

So. I'm considering putting in for a new job, transfer from my med-surg floor to MDS coordinator position with our LTC facility. I'm also about 10 wks pregnant. My current nurse managers know I'm pregnant.
Some factors that play into it: I'm going back to school to complete my BSN (time-consuming, need scheduling flexibility). I already have one kid. In my current position, I'm a lot more "replaceable" than I would be in the niche-type MDS position.

What are the ethics/legal issues of disclosing or not disclosing pregnancy during a job search? If I were looking at something that was not so specialized, I may not be as concerned, but if I'm the only one (or one of two) trained to do the job, then I think I am obligated to disclose even though that seems dicey.

I'd like to hear opinions and personal examples. What do you think?

Tx,
Rebecca (okay not barfing but feel like it most of the time)