I finally gave in last night (five weeks), I had stitches and it was just a little painful.
You could open yourself up to infection but it's unlikely.
I have to say I gave in to sex at 4 weeks and I had stitches and I feel fine.
Not sure what you mean by "surgery". I'll be honest, I have only ever waited 2-3 weeks after delivery to have sex, and they were vaginal deliveries with stitches. I have never had a problem.