I feel it very much depends on what you're subject is.
I shoot wildlife, and therefor you can miss it in normal ways (exposure is off, image isn't sharp enough) but you also miss it because the head is turned, a shadow is going across the side of the animal.... Some of those apply to taking kid pictures as well.
But the other problem is *your* standards. As you get better you throw out images you would have kept 6 months ago.
What I believe happens is that as you get better you just don't take images you would have taken before... this increases your "keeper" rate.
But then you have higher standards and therefor throw out more than you would...
and it averages out to a similar keeper rate.