Ok Ladies so I have a question and need some advice from other moms. My SO and I are moving back to hometown. While…

Ok Ladies so I have a question and need some advice from other moms. My SO and I are moving back to hometown. While we've been away, I have kept in good contact with a few of my peers/co-workers from the hospital I worked at. Last week, I emailed my previous manager on the unit I was working and gave her details about us moving back, also told her I'd like to inquire about the possibility of retaining my position. Well yesterday I get a call from HR, basically skipped over any interview process and like that, I'M BACK IN. She wants me to call as soon as we're back in town so I can come in for all the paperwork, drug screen and orientation etc. I'm stoked about the opportunity, however I haven't told them that I'm pregnant. 6 months pregnant at that. Now my question is, how do I do this?? How do I keep this opportunity to work until I deliver and how do I tell them???