It's not a bad thing that we care more about people we know than strangers that we've never met because we'd go insane if we cared about several billion people with the same intensity with which we care about our own families and friends, but that emotional distancing can be abused to allow people to do terrible things, which is why almost every large scale atrocity involves dehumanizing the enemy.
You can find a good article about how emotional attachment and closeness changes the way people make moral decisions in this article. Basically, see an ultrasound changes an abortion from a utilitarian decision about the fate of an anonymous stranger into an emotional decisions about the life of a person you've seen and know about. It shifts the decision from abstract to personal.
Never forget that the current pro-abortion issue isn’t about keeping future occurrences of abortion legal,
it’s totally about keeping past decisions guilt-free.
Another factor is determining gender early coupled with cultural linguistics: once you can start using “he” or “she” instead of “it”, the reality of the fetus as a true person comes sharply into focus. This is even more so when you can pick and apply a name.
I think It should be added that regardless of the emotional aspect of the decision making progress, ultimately a decision is made be the "will" although it is influenced by the emotions. I think the ultrasound pics enable one make a "reasonable" choice.
Regards
Gonzo