For many people, both men AND women, an abortion is seen as murder, regardless of how long the egg has been fertilized. For them, there is no "fetus" or "embryo" or "zygote." There is only a baby, which for them is always considered a human being. An abortion destroys that fertilized egg. The Roman Catholic Church believes that life begins at conception. That means any and all abortions constitute murder.
Even if they are not religious, those who hold the belief described above, that constitutes murder. If that is their belief, they also believe that abortion is morally wrong because abortion = murder.
If that is your view, you can hardly be expected to say that abortions are a legitimate choice for women to make.
The majority of Americans don't believe that the developing fetus can be called "a human life" until the fetus grows to the point where the baby can survive outside of the mother's womb. Further, they believe that the life of the mother supersedes the life of the baby. In other words, if the mother's life and health is endangered by the pregnancy, then the mother has the right to terminate the pregnancy.
Most Americans believe that the trauma a woman (or a girl) goes through due to a rape or incest is so significant that she will suffer irreparably if the pregnancy is allowed to continue. Therefore, an abortion is an accepted medical procedure to preserve the mental health of the pregnant female. Further, if a woman's life or health is threatened by the pregnancy, then an abortion is an acceptable choice. There are several medical conditions that con occur during a pregnancy which mean two things: (1) the baby likely cannot survive/cannot be carried to term without dying in the woman's womb and (2) the mother's life is likely to be forfeited if the pregnancy is allowed to be continued. For example, a tubal pregnancy (or ectopic pregnancy, where the fetus exists outside of the uterus, such as in the fallopian tubes) will never end in the birth of a live baby, and if it is not dealt with, the mother will most likely die. The medical treatment to resolve this condition is... ready? ... an abortion procedure. [EDIT: As Lady has pointed out, it is not actually an abortion procedure. However, it is a medical treatment that ends a pregnancy, and legislatures and hospital administrators get nervous whenever they are dealing with ANY kind of pregnancy (and this is defined as a pregnancy since it has a fertilized egg growing inside the mother.) The bottom line here is that there are unnecessary delays in many cases, as my comment below illustrates.]
In places where all abortions are illegal, doctors are afraid to save a woman's life because they run the risk of being arrested for breaking the law.. for murdering a child--even though no child would ever result from the "pregnancy."
Who will pay for the prenatal care if a woman is legally obligated to carry a pregnancy to completion? Who will pay for the additional food necessary to feed another mouth in the family? Who will pay for the child's health care as he/she grows up? Will additional funds be set aside for these children if there are genetic conditions or medical and/or psychological complications? Who will provide the funds for the necessary education? Will the politicians who are mandating women to carry pregnancies to term also providing the funds to care for the children after they are born? If you live in Texas, for example, you cannot have an abortion after a fetal heartbeat has been detected (about six weeks after conception.) Yet Texas is dead last: it has more uninsured children than any other state in the Union (almost a million uninsured children.)
Children who are the result of an unwanted pregnancy face myriad issues as well. Not all adoptive parents are good ones. Foster homes are not always good placements for the children. Parents who will not or cannot care for the children they have ... well, that's another whole issue, isn't it?
So... it's a very complicated issue, and not the simple "choice" that either of the two sides might make it out to be.
