Wouldn't it be better to educate them in ways to guard against pregnancy as a first step?
That's a by-product.
Studies have shown that in poorer countries girls that are educated will have significantly fewer children, if any at all, due to them having options beyond "pleasing" a male and becoming a baby producing machine.
Similar to first world really ... those with the intelligence and ability are having fewer children ... so the answer is ... educate the girls