Just in case anyone is reading this years later - the answer turned out to be “As soon as she was born and in my arms”.
Congratulations to you and your husband.
Oh what a happy story!
How are the grandparents holding up, since you said it would be a first for both sides?
Yay, Septima, congrats! And a big welcome to the little lady. 
I know the blessed event has already occurred (grats!), but I thought I’d put in my $0.02 anyway.
The pregnancy felt real right away, since I was getting “morning” (all day) sickness before I even missed a period. However, once he was born it took quite a while before it felt real for me to be a mom, and for him to be my son. He didn’t sleep well, and as a consequence I didn’t either, so it really wasn’t until he was about 9 months old and sleeping longer than 2 hours at a stretch that I got rested up and started to feel like a human again. That’s when everything kind of clicked into place for me.
I just had a funny mental video of someone putting the baby in your arms and you looking up saying “Holy Crap, I’m pregnant!”
but, Congratulations!!