When and how did you tell your employer?

C
I'm so scared to tell my manager - I'm at 14 weeks and my annual performance review is in 4 weeks. I don't want the news to give them a subconscious bias against me (as they will have to pay me for months throughout my leave and I will be transitioning off some major projects) 
I'm not sure how these conversations usually go down and if I should give them the benefit of doubt, but I want to get the best raise and promotion I deserve so I can provide for my baby. I've worked really hard this past year and as much as I want to trust my employer, I need to protect my own interests! 
How and when did you tell? How did it go?