Greetings, kristopaivinen! I notice you haven't been active at Atheist Nexus lately. <sigh> Sometimes it can seem a bit fragmented, with different groups for every interest. Please consider a group for socializing, where we talk about whatever's on our minds, Hang With Friends. :D You might feel more at home, and not want to drink as much.
My definition of “an-abortion-that-should-have-been” is one where the mother was prevented from having an abortion that would otherwise have taken place. In other words, the pregnant woman did not want to continue with the pregnancy and there were sufficient predictors of future problems (financial, educational, caring ability, emotional fitness, fetal/child disorders and deficiencies) for abortion to be the best choice in the circumstances. In such cases of forced pregnancy the outcome is relatively poor for all those involved: mother, father, siblings, relatives and the eventual child/teen/adult.
By the way, you are falling into the common “pro-life” trap of assuming that all, or most, medically induced abortions are provided to single women who were not using contraception and who do not have other children. In like manner, you also assume that no-one but the pregnant woman would suffer as the result of the birth of an eventual child. It may surprise you to know that the demographics include a huge proportion of married woman with children who have experienced a contraceptive failure. The decision to abort the unexpected pregnancy is usually taken in consultation with the woman’s partner/husband and, sometimes, in consultation with older children in the household.
Decisions of this nature are necessarily based on statistical probabilities rather than certainties. This is true for most of life’s major decisions, including other types of elective surgery and medical procedures. The projected risks are weighed against the projected advantages. The easy decisions are those where death or devastation is the certain outcome of a particular course of action.
There are, or at least should be, a whole range of factors which the host and her doctor consider in the course of deciding whether or not to medically terminate a pregnancy (as distinct from the far more prevalent “natural” abortions which happen in their millions every day).
Whether the pregnant woman would grow to love the resulting child is not usually a terribly salient or important factor in the equation. (Hormonal changes after birth would predict that she would probably would.)
The most relevant questions generally pertain to the realistic resources which will be available for caring for the child and the effect which the birth (often not the first one) would have on the resources available for the care of others in the family. When there is competition for resources the sentient have precendence over the potentially-sentient..
Other relevant questions involve the life and health of the host. A related question is the effect of the host’s death or impairment on other parties he mother/care-giver, the quality of life which could be predicted for all those involved (not just the potential person) and the risk of death, pain and serious medical problems for the host (pregnant woman) if the pregnancy is allowed to continue.
There is also the case where it is certain that the fetus is going to die at some time during the pregnancy or shortly thereafter and the mother’s health and well-being are increasingly at risk the longer the fetus is allowed to continue developing. An example of this would ectopic pregnancies.
In case you aren’t familiar with the details, this is when a fertilized egg does not make it to the womb and grows in the woman’s fallopian tubes. The fetus has zero chance of surviving but the mother will experience excruciating pain, never be able to have children again, or die if it is not removed quickly.
On one side of the equation is the life and quality of life of a conscious, feeling person whose death would grievously and significantly affect the lives of others (husband, dependents, family, friends) plus the well-being of all those just mentioned. On the other side of the equation is a mass of cells which only has the potential to turn into a conscious feeling person at some time in the future. Making the choice should not be difficult unless you have religious baggage which gives the cell bundle an elevated value compared with the conscious beings involved.
I think you have the legal part of your argument backwards. Those arguing that abortion should never be permitted in any circumstances are the ones who wish to enforce arbitrary decisions on everyone. They are also the ones who have caused the “arbitary” legislation to come into existence in the first place. There are countries where there are no laws restricting medically induced abortions and the decision to abort a pregnancy is one which is made under the same circumstances as any other kind of surgical procedure which has ramifications for the person’s future health and well-being. In these countries a decision to abort, or not to abort, can be based on the full range of known, predictable and hypothetical factors which impinge on the outcome.