There are a lot of religious arguments (and general political ones) against abortion. But I think that the argument, generally speaking, demonstrates the scientific illiteracy of the everyman.
So you're against abortion for whatever reason, but consider this argument from Neil DeGrasse Tyson:
"Most abortions are spontaneous and happen naturally within the human body. Most women who have such an abortion never know it because it happens within the first month. It is very, very common. So in fact the biggest abortionist, if god is responsible for what goes on in your body, is god."
Now when he says 'very common' what he means is 50-70%. That's 50-70% of all pregnancies end in a spontaneous abortion that you 1) can't control and 2) are never aware of.
So how is the anti-abortionist stance tenable given this dataset?
There are two issues brought up here.
1. Comparing (assuming first we blame God with all natural events) God's sovereignty with ours.
2. How can we determine or attempt to do so whether abortion is right or wrong.
1. As for the first one. We must start by assuming something we can not know and which is irrelevant either way. I think it theologically unsound to attribute to God's preference or active will all natural events. The bible does not say and never suggests that God actively causes al events that occur. It merely states that God is aware of all events. However either way this is really irrelevant. Comparing our limited knowledge and lack of any ultimate sovereignty against God's complete sovereignty and infinite knowledge. It is infinitely more absurd to do this than it would be for an ant to judge whether Newton got calculus right. It is simply a meaningless issue which we are not equipped to know or judge.
2. The second point is more meaningful. I have often wondered if there is any way in a secular sense to attempt to determine whether any position on abortion is sufficiently justifiable. There is no way without God to know whether any opinion about abortion is correct or not. In fact without God there is no objective rightness concerning abortion for our opinions to be judged. However there is a method by which we can justify a position on abortion without any certainty if we are right or if there is any actual right to be.
A. Given the fact that society must (or at least will) produce some laws to govern moral issues such as abortion I will not bother to justify our need to have some rules of some kind.
B. So granting we must make laws of some kind in this case how can we justify any law we make.
1. It is abjectly absurd to debate any time frame which the day previous it was morally excusable to kill a life in the womb, and the day after it is completely morally reprehensible to do so. To do so requires making so many arbitrary assumptions that whatever is produced is completely contrived. So the only relevant issue is whether abortion at anytime is justifiable or not.
2. Neither the atheist or the theist has any certainty what so ever whether taking a life in the womb is morally excusable or not. (By the way this only concerns taking a human life for the sake of convenience, to do so for the sake of medical necessity is an altogether different animal).
So the issue comes down to this in general.
Those who support abortion and are traditionally more secular minded have no way what so ever of determining if abortion is justifiable or not. However this group gambles on death for the sake of convenience despite being in complete ignorance. The most common and deplorable justification for doing is usually some mysterious rights granted to the mother, but which exact same rights are denied to the fetus, despite having the theoretical basis for either party having any inherent rights of any kind. This is not a position founded in sufficient reason, but is instead founded in preference and hypocrisy.
Those who deny abortion and are traditionally more theologically minded and likewise have no way what so ever (in a secular sense) to determine if abortion is excusable or not. This group (granting the ignorance) gambles on life instead of death, and does not let self interest in their own convenience wrongly justify the taking of another's life. This group despite having a theoretical basis for inherent rights does not strip the exact same rights from one individual by demanding it for the other but consistently grants both individuals the same rights.
Neither group's position is grounded in certainty but only the latter group is grounded in reason.