While I completely see where you're coming from here, this is not a one-size-fits-all situation. I specifically chose to get pregnant in grad school from the sheer flexibility of the situation. 1) Aside from about 6-8 hours a week, I can be with my child without paying the outrageous day care costs in my area 2) I prefer to work from home anyway 3) I have breaks.
Of course you can't plan everything but I imagine I'd be far worse off if complications arose and I could not work at all and we were banking on that income. While I do work as a research assistant, it's a far more flexible, lax working situation than any "real world" job I've ever had, one I can do from home. Because I get paid, yet still have all this flexibility, I'm far better off having kids now rather than when I need to pay for full time day care. That still allows me plenty of quality time with my baby on the way.
Just an alternative viewpoint. :-)