The only point I have to discuss that hasn’t been covered (often including gratuitious insults!) is that for a small portion of the population, the illegality of abortions would actually lead to a decrease in number of children people choose to have.
Example:
My family history includes a genetically-transmitted, hideously debilitating, untreatable, grossly painful and ultimately fatal disease. As it is a genetic disease and there is a possibility I, personally, am a carrier, without the reassurance the legality of abortion gives me, I would in all likelihood refrain from ever getting pregnant.
If I know there is a possibility I am a carrier, and there is a possibility my husband is a carrier, rather than risk children who are affected, we may very well decide NOT to play Russian roulette with the health and welfare of our offspring at stake. This does not seem to be to be an amoral choice.
Take an individual who has a parent who died from Huntington’s Disease. That person has a 50/50 shot of developing the disease herself. However, she might not actually develop noticeable symptoms until well into her 30’s - plenty of time to have children. The question is, does a person with Huntington’s cut themselves off from ever having children? Or do they just ensure that they have no children WITH THE GENE that causes the disease?
Additionally, consider that there are a few fatal genetic disorders associated with distinct cultural groups. Tay-Sach’s Disease, Machado-Joseph Disease, Familial Dysautonomia, Canavan Disease, to name a few. If all those people chose not to reproduce, that would spell disaster for the cultural groups they are associated with. If there is no safety net (and speaking as woman with a family history of a fatal genetic disease, in that situation an abortion, while hideous to contemplate and not something I want for myself ever, is definitely a safety net) in the form of an abortion if you discover your unborn child is afflicted, then how many of the people in those cultural groups will choose NOT to procreate at all?
There are hundreds of diseases that are genetic. (For a list of some of them, please see: http://dmoz.org/Health/Conditions_and_Diseases/Genetic_Disorders/ - pardon my technical ineptness if the link doesn’t work :P) Not all of them are fatal, but a goodly percentage of them are. In the cases of the fatal genetic disorders, a fair proportion of them are not IMMEDIATELY fatal. They are ultimately fatal - but in some cases not until the person affected is past childbearing age. The ones that are ultimately fatal are almost-inevitably fatal after an extended period of unbelievable suffering.
People with a family history of a fatal genetic disorder are faced with the decision of whether they would like to procreate and risk their child suffering that fate, or not procreate at all if the option of an abortion is removed from them. I personally would likely choose not to procreate. Some risks aren’t worth taking. Particularly if I’m taking them for someone other than myself.