I'm sorry you had to make that choice years ago, but there is no real point to suffer endless guilt trips over the situation and those who would keep lashing you are being unkind.
It is a choice made by many mothers each and every day and although in my heart I do feel it is wrong (there may be exceptions - I can't think of any specifics at present), I can understand that some feel the need to abort the child and have to live with the consequences for doing so.
Friends of mine chose to abort a child a few years ago due to poor financial circumstances and feeling that it was not the right time for a baby due to career choices. They asked me what I thought about the decision to my face and rather than lie, I tried to express myself in a truthful yet caring way. Unfortunately there is no easy way to tell somebody under those circumstances that one thinks that they were morally wrong to do so and the conversation ended up in the midst of awkward emotions.
It is a highly emotive area, but ultimately it is up to the parents involved to make that choice and not for me or any human (IMO) to ultimately sit in judgement, although we have the right to voice an opinion.
I think under similar circumstances, if I were forced into that postion I would choose the fostering option.
I hope you feel better about yourself soon and find a loving expression to give to others from within the pain you bear.