I have made up my mind that I will not be returning to work after baby is born. I won't take maternity leave either because I don't feel right pretending like I'll be back when I have no intention to. 
So now it's a question of timing. When would you say something to your boss? Immediately? Wait until July? Somewhere in between? 
The part of me that wants to wait is the part that still can't believe I'm pregnant! I don't know if I ever got over the whole "don't get too excited. Wait and see" attitude of the first trimester.
Thanks for your feedback!                
                             
        
Re: If you're not returning to work, when to tell?
This really depends on your situation. I would say that if you're entitled to paid maternity leave, take it first, then tell them. I know some states don't allow this, if you don't return to work, you have to pay back your maternity leave. I'm in New York, and my maternity leave was my Short Term Disability policy.
I think that using STD for 6 weeks is totally acceptable, you're recovering from birth and have worked for this benefit, so you should get it.
For myself, I didn't know I was going to stay at home until the end of my leave with my 2nd child. I ended up going back to work for 1 week, then putting in my 2 weeks notice (after a 6 month maternity leave).
son#1 born 6/2010
son#2 born 4/2012
son#3 born 7/2014
My employer has been pretty good. I'm going on 10 years with them. Another person in our department has been dying for a promotion, so my leaving might help open that door for her.
I think I'll just wait on it for a while though. When it comes closer to July, I might start preparing them for the possibility that I might not return.
It sounds like my work makes you take the 6 weeks of maternity leave first and then the Short Term Disability, followed by vacation & personal days. I wish I could flip those around and go straight to the sick days + disability. I feel entitled to those benefits, but not to the mat leave.
I agree with some previous posters...I think it depends on your work situation. In my previous job, the hiring process was very lengthy. It would take a minimum of three months to get someone hired. So if I knew that far in advance that I wasn't coming back, I would let them know sooner rather than later so they had enough time to hire a replacement. Also, it depends on whether you plan to re-enter the workforce at some point and what kind of impression you want to leave on your employer.
ETA - If you told them at the beginning of July, that would be 5-6 weeks before your due date. That's cutting it a little close for me if you are sure you aren't coming back. Every company I've worked for has paid me for my vacation days upon termination of employment. I would think your company will do the same.
BFP - 01/04/2016; EDD - 09/15/2016 DS #1 - 07/2014
I get 5 weeks paid 100%, 3 weeks at 60% and 4 weeks unpaid. If I decide not to come back, I will do so in the last 4 weeks to give them time. They will be hiring a freelancer in the meantime so the option to hire that person can be there too. I'm also switching to my husbands insurance since he works for the state and it's dirt cheap, so once the baby is born (qualifying event) we don't have to worry about paying the company back, etc.
Personally, if I knew I wasn't going to come back, I would give 2-3 weeks notice, so around 37-38 weeks. If I went into labor and baby were born early, I would tell them then. I agree that it's not fair to wait until the end of your maternity leave, but I think you really need to look out for yourself first. Your boss will understand -- 2-3 weeks notice is fairly standard and considered plenty professional. You'll be wrapping up projects anyway by then.