You have definitely heard a lot about one-child policy which has been successfully implemented in China, for example. Well, there is a belief that it is not quite ethical to implement such policies as one cannot control how many children a couple wants.
Yet, there are some really good points which should definitely be mentioned in this respect. For instance, it is one of the most effective ways to control population growth. Besides, the latter has become a huge problem nowadays as the population of the planet is growing and soon enough we will not be able to provide enough food and housing for people.
That is the reason why implementing a one-child policy seems like a great idea, to say nothing of the fact that people need to be educated regarding the ways in which it is possible to prevent unwanted pregnancies. What is known for sure is that we need to figure out how to deal with the problem of population growth and we need to do that as fast as possible.