Probation period work :?

Hey. I am really hoping someone will be able to answer this for me. I live in Alberta, am almost 18wks pregnant and just started a job about two and a half weeks ago. They dont kno I'm pregnant yet as I am just starting to show, I'm really worried about them letting me go when they find out because of the probation period thing. I'm wondering if they are allowed to fire me for being pregnant. The company I am working for wanted to hire someone that would commit a year to them which I may do by taking a very short term mat leave but I kno the last girl that worked there was pregnant and they had talked about all the money she cost them due to mistakes she started to make closer to the end of her pregnancy and I'm worried that they will just assume that I'll be the same or they will be mad that I said I would be able to commit a year (just because I'm undecided on if I'll want to take mat leave or not) so basically. Can u be fired on ur probation period in Alberta. I've tried searching this but havent found exactly what I'm looking for. :? :? :?