Starting a new job at 13 weeks

I currently only work part time and they do not offer any kind of benefits including maternity leave. I also hate the type of work I do (call center type) so I have been looking for a new job since i got this one. I have an interview today for a full time position that will offer benefits and better pay, but I'm worried that if I tell them right away that I'm pregnant, they won't hire me. So, should I wait until after I sign all paperwork before telling them? I'm certain they are going to be hiring me based on the fact that I was hired there years ago, but had been offered a position with a different company first that I had accepted, so I turned out down last time. Plus, they already removed the job posting 😅 Should I wait for a few weeks? maybe after training? Training will be 4 weeks and I'm pretty sure I can hide my growing middle fairly well (since I will forever have a "pooch" from my previous pregnancies)