New job, when to tell them I’m pregnant?


So, I just got a new job a week or two ago, I’ve yet to start as I had to wait for my background check to clear and I have to complete training before I can start. I found out two days after my interview that I’m pregnant. This will be the best job that I’ve had since I started working and I’m really looking forward to it. I’ll have a perfect schedule, weekends and holidays off, PTO and benefits, I’m just worried about missing any work for doctors appointments because for the first three months I’m on a “probationary period” and I don’t want to miss any work and make myself look bad. I’m just wondering when I should tell them that I’m expecting, and do you guys think that missing work for appointments will go against me during my probationary period?