What is murder? it is "The crime of killing somebody: the crime of killing another person deliberately and not in self-defense or with any other extenuating circumstance recognized by law." Certainly killing someone at random who has done no harm can be declared as murder. The difference is that this person does not depend on another human to survive in the way a fetus does. The person killed who was already born had a conscience, thoughts, and opinions. But, what is a human for that matter?
Supporters of abortion describe an unwanted fetus as a parasite. It feeds off of its host to survive. Is the killing of a parasite which has the potential to be a human then acceptable? Thus far there is no sure answer. Certainly ethics can come into play and what feels wrong according to ones own morals can be the main factor. It should also be noted that many strong believing pro-life advocates turn to abortion if facing an unwanted pregnancy themselves.
A large issue, and peraps the most significant is that even if there are anti-abortionists who declare it to be murder, does that give them the right to enforce their belief on others? This can fall into another form of ethics altogether.
China, being a very high use abortion nation, offers abortion very cheaply and in a nation which cannot support all of the unwanted pregnancies being brought to fruition. If all of these fetuses were born, there would be a larger need for food and other necessities. The increase in burning of resources would quickly lead to massive economic problems later on. In these ways, abortion has helped to conserve economic stability. This is a very brief and little depth summary, but there are always to be different positives and negatives in the minds of each individual in regards to this topic.