When did you return back to work?

I got hired at a new place yesterday t requires a 90 day probationary period. I have 4 months left in my pregnancy so I barely made it. I didn't tell them that I was pregnant nor did I tell them that I had a doctors appointment on the 29th. Can I not request it off because it'll be within my probationary period or what? I was hoping to come back to work within 2-3 weeks of having my baby but idk. I know some people wait 6+weeks but I'm not sure.