I couldn't agree more. I always say this and I think it is very important to emphasize that giving birth to child with poor economy and environment does not just bad for the parents but also to the child. Long gone are the times when it is okay to have birth and see where everything goes. Today, family planning is vital to ensure the child and the family's future.
It is very logical indeed when a family is in economic difficulties actually having many children is something that will make the family worse off, this even applies to a country, a poor country will find it more difficult when the population addition does not match or is in line with the per capita income of the population .
There is no other solution apart from family planning which limits children in a family, as far as I know there are several countries that implement this.
China once had family planning rules implemented for the whole country where a family couldn't have more than a particular amount of children because their population was increasing significantly, they are still the most populated country in the world but they have controlled the birth rate very well which was increasing rapidly before such a rule. So it surely can be destructive for a country's economy if the population is crossing a sustainable limit.
Generally, when a family has financial issues, they will think of this thing themselves that they shouldn't have a lot of children because they won't be able to feed them all, but when a family has no such issues, they would barely think of the economic advantages or disadvantages unless there is an official rule of not having a lot of children.