While I cannot speak from experience, I think this topic is large enough to write fairly generally and not be far from truth.
I think first, the mother of the unborn child is most affected by abortion. The physical pain of an abortion can last many weeks - but the emotional pain can last a lifetime. Most women who have had abortions will testify that (whether they regret the action or not) it is something they will never forget - and do not have pleasant memories of.
Those who believe life begins at conception believe the action condemns an unborn life and soul to an unnecessary premature death.
Finally, other family members and friends would certainly be affected. Anytime a person undergoes a major life decision or change, whether positive or negative, others who love and support that person are in part, affected. If the father is aware of the abortion - no doubt he could experience similar feelings and thoughts as the mother. The most prominent of these feelings is probably grief and wonder if they made the right choice.
The Catholic church has taken a firm stance AGAINST abortion. In any instance where the abortion is deliberate and not done to save the life of the mother - it is considered a sin - namely murder. It is certainly forgivable, according to the pope - but considered unbiblical and evil.
The teaching of the Catholic Church on abortion is that it is never morally acceptable to abort a fetus intentionally. This is true even in the case that the mother's life would be in danger if she were to try to give birth. We can see this in the following quote:
The embryonic child, as seen above, has a human soul; and therefore is a man from the time of its conception; therefore it has an equal right to its life with its mother; therefore neither the mother, nor medical practitioner, nor any human being whatever can lawfully take that life away.
As to who is affected, I would imagine that a wide range of people are affected. If you consider the fetus to be a life, it is clearly affected. The mother is surely affected both physically and emotionally. Depending on their relationships (on whether they are close) and their knowledge of what is going on, anyone who knows the mother could be affected as well.
The Catholic Church is opposed to abortion. It believes that the unborn child in the mother's womb has a soul and abortion would mean the willful and deliberate killing of a person with a soul. Abortion according to the Catholic Church is synonymous with murder.
The first person to be affected by the decision to abort the child would naturally be the mother. Physically she has to bear the trauma of the abortion - hospitalization, pain, excess bleeding etc. There are many cases in medical history where even with the best medical care abortion has proved to be fatal.
Secondly, the mother and her partner would be tormented by feelings of guilt as to whether they have actually committed murder.