Although in Islam there are debates about the nature of Jihad and legitimacy of carrying out attacks in the name of Allah, there is not that much of a debate about whether Muslims ought to practice abortion. The general consensus is that abortion is haram, forbidden.
The reason offered for the prohibition against abortions is that the child is already “ensouled” in the womb and has not yet done wrong. There is disagreement about when “ensoulment” happens in the womb. Some schoolsof Islamic thought place the date at 7 weeks into the pregnancy, while others would say that ensoulment occurs at the moment the child begins to move inside the womb (around 12 weeks or so). Probably the majority of Muslims accept the 120-day mark because it is established in the Hadith literature (Sahih Bukhari, Volume 4, Book 55, Number 549).
In that Hadith, there is a revelation concerning what we might call predestination. According to this Hadith, an angel of Allah will enter the womb and write down up
on the child all of his destiny—including how long he will live and whether he will end up in Paradise or in Hell. Thus, Muslims conclude that after this point, the life is fixed and must not be ended.
Prior to the 120 day mark, Muslims argue that there are a couple of extreme cases which may require an abortion. On the one hand, if the mother’s life is in serious danger, then the child must be aborted because the mother is already functioning and fulfilling duties for the family. Thus, if one or the other must die, then the child must die, not the mother. Note that this provision is not the same as that which has prevailed in the U.S. since Doe v. Bolton enshrined a very broad definition of abortion with regard to the health of the mother. Under Doe, a mother can procure an abortion based on the stress that pregnancy causes. This is not the case with the Islamic exception for the safety of the mother.
The other extreme case in which abortion may be allowed is the case of severe fetal deformity. Muslims are not unanimous in considering fetal deformity a justifiable cause of abortion. However, many Muslim scholars argue for the legitimacy of abortion if the child in the womb is severely deformed. In this case, again, the 120 day rule remains in effect. And, the fetal defect must be diagnosed by two Muslim doctors before proceeding with the abortion.
Again, few will quote the Quran in favor of abortion because abortion deals with human beings who have not yet committed any injustice against Allah. Surah 5:32—though it does not directly speak to abortion—does guide Muslim thinking in the matter. In that Surah of the Quran, Muslims are taught “that anyone who murders any person who had not committed murder or horrendous crimes, it shall be as if he murdered all the people.” In other words, killing an innocent in the womb would be to the Muslim mind the equivalent of killing off a part of humankind.
Though Surah 5:25-35 is about justifiable killing for those guilty of murder or “horrendous crimes,” it speaks to the nature of the entity in the womb—namely, that it is human. Indeed, it is considered a form of innocent human life and, thus, deserves to be protected. Some Muslims will quote Surah 17:31 as a further—and stronger—argument against abortion:
Kill not your children for fear of want: We shall provide sustenance for them as well as for you. Verily the killing of them is a great sin.
Granted, this verse appears to speak of children already born, but it is often recited in defense of forbidding abortions. Clearly, the text is teaching the mother (or parents) not to be anxious about providing for their children. Whatever temptation they might feel toward getting rid of their children as a result of poverty, they must put that temptation out of mind. Killing children is a great sin because children have not yet resisted Allah or committed murder or any other horrendous crime.
This verse, then, along with the Hadith quoted above and Surah 5:25-35, make it plain that the general disposition of Islam is to oppose abortion. As Muslim scholar Abul Fadl Mohsin Ebrahim concludes regarding Surah 5:32,
“From this verse it is evident that every human being has the right to be born, the right to be, and the right to live as long as Allah… permits. No one may be deprived of life except for a legitimate crime…. The fetus is regarded by all schools of Islamic law has having the right to life, as indicated by the fact that the death sentence on a pregnant woman can be carried out only after she has given birth.”
 Abul Fadl Mohsin Ebrahim. Abortion, Birth Control and Surrogate Parenting: An Islamic Perspective. n.p.: American Trust Publications, 1989.