I also do not know what the answer is. Actually, I know that there will never be a complete answer to the problem as long as this old world stands.
However, there are partial answers, and some are better than others. Sad situations like jacqui c describes have always occurred and will always occur, but they occur more often in some sub-cultures than in others and more often in certain periods of history than others.   
Birth control has been readily available for a long time. Unwanted pregnancies are still occurring. What we, as a culture, have been trying for the last 4 decades hasn't worked. Why would it start working now?
Kent