All political and/or moral philosophies have a common thread of pacifism. This states that it is generally wrong to harm another person. "Person" here refers to a member of your moral community.
Some philosophies have a small moral community, often restricted to one race, creed, nationality, or religion. Others expand their moral community to all living things (though they often ignore the fact that a living thing can be a non-animal). Another philosophy falls somewhere in between, stating that each species is its own moral community, and that every organism has a moral obligation towards its own kind.
Another thing that makes moral philosophies is how lax they are on the "generally wrong to harm another person". Sometimes, violence is allowed if it supports some kind of greater good. Sometimes, violence is never justified.
Sometimes, "harm" is defined very narrowly to physical harm. Sometimes, emotional abuse is thrown in. Still other ideologies (such as communism) see economic exploitation and/or denial of basic services (police, fire station, health care) as a form of harm.
Whichever one of these you subscribe to, the common thread of "do no harm" is there. But what defines a philosophy such as left/right, libertarian/authoritarian is not the scope of the moral community, but the scope of "generally wrong" and "harm". The definition of "person" is more or less up to the individual. Whatever the scope of the moral community, that determines the definition of "person". The definition of "person", combined with the scope of "generally wrong" and "harm", is then plugged into the combining thread of pacifism to determine the application of a belief system.
Because of this, the anti-prenaticide position is compatible with any belief system. This is why you see such groups as Democrats for Life of America, Libertarians for Life, Feminists for Life, the Society of Pro-Life Agnostics and Secular Humanists, the Atheist and Agnostic Pro-Life League, the Pro-Life Alliance of Gays and Lesbians, and others.