Congrats first of all Hope everything continues to go well for you!

An employer can't not hire you because you are pregnant i'm pretty sure, i guess it's up to you if you want to tell them. If you get a job offer in the next few weeks its still early days in your pregnancy so you mightn't want to say anything to anyone and when you do tell them down the track you don't even need to say if you knew when they offered you the job. If you decide to tell them straight up just be honest and say how long you are wanting to work in your pregnancy and go from there, who knows they might have a short term position they could offer you.

Good luck with whatever you decide