I was the mom who coded while breastfeeding and had her son at his first LUG meeting before he was two months old. Being a mom and being a hacker have always melded pretty well for me, despite the fact that I'm now a single mom: my now-8yo likes tech conferences and has even spoken at one, he comes home from school and does his homework in my office while I do my work, he's even made dinner on one or two evenings when I was really swamped (okay, it was chicken nuggets and macaroni or reheated leftovers -- but I didn't have to cook it!). He's my mini-hacker, and he says he wants to grow up to be an inventor.
I highly doubt I'd have pulled all that off if I were like a "normal" first-time mom. Luckily, I grew up in the sort of family where older cousins look after younger cousins -- as a teen I even moved in with relatives to be nanny to their kids for a while when their work schedules had them away from home too much.
Juggling a start-up and a young child is quite possible, but it helps to have some experience under your belt, and to include your kid in your working life a bit. Instead of having two lives competing for your energy, you get a kid who understands what you are doing and why, and feels part of it rather than left out.