Limit the number of children? Yes. Of course, because it's almost traditional or cultural: in poor countries the large families are normal. But are the large families the cause of the poorness? I think not. At least not the main cause. I think that the main cause of poorness was the savage colonialism and the following dictatorial governments.
European colonialist countries took out raw materials, using as cheap labour to the inhabitants of those countries or directly slavery. Later came the dictatorial governments that causally they enriched the domes of their governors and condemn their people to poverty.
One of the principally wish of these dictators is maintain the ignorance of people to get all the wealth possible including the religious fanaticism.
One example of this is Egypt and Mubarak. This person is one of the richest men of the world while Egyptians are swimming in the poorness. Or the Libyan dictator Gadafi who has properties all over the world.
There are other kind of poor countries as for example countries without natural resources or raw materials. This is another theme.