Most Christians, and many other theists (God-believers), consider abortion to be the murder of babies. And perhaps as many (or more) are opposed to the euthanasia of the elderly as murder of those at the other end of the age spectrum. These believers would consider themselves firmly in the “pro-life” camp.
Almost everyone is pro-life for some parts of the age spectrum from conception to death. Ten years of age might find almost 100% totally opposed to their killing. But how many people are equally opposed to killing humans, no matter what their age?
Many Christians who would gladly adopt the “pro-life” label seem to place a somewhat lower value on the lives of young adults, the ones who are sent to fight and die in war. They applaud the United States’ military incursions in other countries and consider the loss of young life a worthwhile price for whatever is being accomplished. Their prayers for the safety of military youth do not include the military youth of the invaded countries. Evidently, the value of U.S. life is considered higher than that of other ethnic or national groups.
I’ve not always been equally pro-life for all humans of whatever age or location, but I am now.