Women have to give up more than men. Guys can spend their 20s, 30s, and even 40s working nights and weekends to build the foundations of a successful company, with the goal of starting a family after they've 'made it'.
The window of opportunity for women is a lot narrower. If you're a woman entrepreneur in your 30's and want to eventually start a family, you'll have some much tougher choices to make than a guy in a similar situation.
I know people have done it before but I couldn't imagine going all out on the early days of building a startup while having to care for a baby, as a father or mother.