Pregnant and New Project Dilemma

I currently work for a contracting company and my project ends in December. Due to the company structure, all that means is that I need to find a new project to work on -- I don't lose my job or anything like that. Since we found out about the December end date, I've been interviewing with different projects. I am about 13 weeks pregnant (due in April) and since it's still pretty early, I haven't told anyone at work.

My predicament is that someone approached me today to be submitted as a Key Personnel role for a new project. It sounds like a great fitting role but as I understand it, being bid Key means that I have to work on this project if we get the work and timeline for award is not always known.

They would be building a team around me as a project manager and I'm feeling weird about it knowing that I would only be there for 4 months before taking a 6 month maternity leave. I don't want to hurt my career by telling them but I also feel bad keeping it to myself. Thoughts?