Well, congratulations of course

And I'll echo those who have said that it depends on you, your better half and your respective schedules. It also depends on the wee one, as no two are alike.
After the birth of my first child, I only gamed about four times during the first two years of her life, following which things got back to normal. That said, I didn't
want to game during that time - I just wanted to be with my little girl. My son was born last year and he is now just over three months old. I haven't gamed at all since about a month before his birth (apart from an Xmas one-off). This time around, though, things are a little different and I am about ready to start gaming again in the next week or so. Unlike with my first child, I am now the primary carer and spend all day with my boy, so I don't feel the need to dedicate every spare evening to being with him (when my daughter was born, I was working full-time in a crazy demanding job and every minute outside the office was family time). So things change from child to child.
A simple (if somewhat trite) answer is that only you and your family can set the timing. You'll know when it's the time, just as you'll know when it's too soon (and if you don't, your other half will doubtless let you know...)