Getting a job while pregnant

Hi all, I am currently 6 months pregnant and I just got a job offer at walmart as a pharmacy tech part time. I already did the drug test and background check, just waiting for it to go through. It is noticeable that I am pregnant but I didn't mention this to the pharmacy manager or personnel so now I am wondering what is going to happen once I start working and they find out that I'm pregnant and will have to take leave after a couple months. Will I get fired for not letting them know beforehand? Any thoughts, guys? What should I do?