On issues like these, a distinction has to be made. There is 1) the Church's general position, and 2) how we should respond personally when someone we don't really know does something.
Regarding the general position (1), the Church has always been against abortion. John Noonan argues that some early Christians gave some leeway based on how many days it had been since conception (ie. some supposedly thought that the soul didn't enter the body until a certain point after conception), but I've never seen any substantial evidence to back this idea up. In fact, already in the first century, the Didache specifically condemned abortions (Ch. 2).
However, regarding how we are to respond to someone who has an abortion (2), it's really not our place to condemn a person. That doesn't mean that we can't say "abortion is wrong," it just means that we shouldn't think ourselves able to pass final judgment on someone as though we are God. One thing that should remind us to think twice before opening our mouths is that there are exceptions that are sometimes allowed, for example when the mother's life is in danger the child may be lost (though this wouldn't be an intentional abortion so much as the loss of the child).
All abortions (spontaneous, intentional, and ones to save the Mother's life) all can cause great spiritual, emotional, and physical harm. It is our job to help a person in such a situation and pray that they can heal. There are people appointed to be "authorities" in the Church, who "watch over souls". It is they who have the responsibility of dealing with these tough issues, hopefully being led by God and a clear head.