One might think it would be the smart people who realize that putting more time and resources into a smaller number of children would guarantee better reproductive 'success'.
That is what I wonder, as well. 
In general, I'm not sure that contributing to a rise in global population is necessarily a good thing no matter how intelligent those children might be.
Children need time and space, just like adults. I think that current trends in raising children tend toward more  hovering and micromanaging and less space and free time. Kids need time away from authority figures and scheduled activities so that they can just be themselves and make their own mistakes.
As the world population grows and as technology becomes more important and more complex, we'll need 
more smart people, not less. The number of tasks that benefit from being done by a smart person will grow, not decline. If there are fewer smart people available to do them, quality will suffer. This is just a fact, not a political statement or some kind of judgment.