There are two specific lines of argument typically used to argue against the right to seek an abortion: (1) religious values that condemn abortion as a "sin"; and (2) ethical concern for the fetus (Reiman, 1999). The first basis for objection is absolutely impermissible under modern U.S. Constitutional law (Dershowitz, 2002; Edwards, Wallenberg, & Lineberry, 2008). That is simply because the First Constitutional Amendment expressly prohibits the government from making any laws of religion. The religious beliefs that "life begins at conception" or that "every human life is created in the image of God" are perfectly acceptable beliefs that are (also) protected under the 1st Amendment. However, no religious beliefs of any kind may be used as the basis for secular law in the U.S. (Dershowitz, 2002).

The second principal argument against abortion is that it is cruel because it causes pain to the fetus (Reiman, 1999). That particular objection is valid in principle (as a concern) but it is invalid scientifically until the point of gestational development where the fetus becomes capable of sensing pain and discomfort. There is no ethical issue prior to that point of fetal development. Once the fetus develops sufficiently to sense physical pain, there is an ethical obligation to eliminate that pain. However, there is not any ethical objection to abortion...

Many people believe that there is a more important moral obligation not to force women to bear children they do not want because that is unfair to any child born into that situation instead of into a loving home where the child is genuinely desired and loved.
There is no valid justification to oppose abortion as a solution to unwanted pregnancy. However, abortion should not be used callously as nothing more than another form of last-minute birth control. Abortion procedures can be dangerous to the woman and they are very expensive to the community since they require medical services, and in some cases, publicly funded resources. Currently, they may also result in fetal suffering in some cases because anesthesia is not widely used during abortions and some abortions are performed after the point where the fetus is sufficiently developed to experience pain. In general, abortion cannot be restricted because it is protected under constitutional privacy principles. However, that right should not be taken for granted or abused callously.

References

Dershowitz, a. (2002). Shouting Fire: Civil Liberties in a Turbulent Age. New York:

Touchstone.

Edwards, G.C., Wallenberg, M.P., Lineberry, R.B. (2008). Government in America:

People, Politics, and Policy. New York: Longman.

Reiman, J.H. (1999). Abortion and the Ways We Value Human Life. Lanham: Rowman & Littlefield.