The Jewish faith is based upon a body of commandments that includes the seven Noahide Laws and 613 parochial commandments. These laws are interpreted (but not altered) by a vast body of rabbinic opinions and case law called Halakhah (The Talmud), which is based upon divine revelation.
The Old Testament contains the seven Noahide Laws in Genesis 9:6. The third law (Thou shalt not kill) includes the admonition, “He who spills the blood of a man in a man, his blood will be spilt.” The Talmud (Sanhedrin 57b) defines “a man in a man” as a preborn baby in his mother's womb. This passage specifically says abortion is a capital crime, a view supported by one of the leading sages of The Talmud, Rabbi Yishmael.
Maimonides, the great 12th-century interpreter and codifier of Jewish law (in his interpretation of the Third Noahide Law) writes in his Mishneh Torah that abortion is a capital crime for Jews: “A descendant of Noah who kills any human being, even a fetus in its mother's womb, is to be put to death.”
Maimonides ruled abortion allowable only if the pregnancy definitely and without question endangered the life of the mother (Hilkhot Rozeah 1:9 and Shulhan Arukh Hoshen Mishpat 425:2): “The Sages’ rules [regarding] a pregnant woman in hard travail that it is permitted to dismember the fetus in her womb, whether by chemical means or by hand, for [the fetus] is as one pursuing her in order to kill her.”
This passage refers to “hard travail,” a delivery complicated by the size or position of the baby, so that a normal birth was impossible. At the time this commentary was written (before the development of obstetrical forceps and, later, safe surgical techniques for a Cesarean section), this kind of problem often resulted in the deaths of both mother and baby. The only way to remove a baby who was “stuck” was to dismember him. In most cases, the mother would have been in labor literally for days, and the baby would have died from anoxia.
In summary, The Talmud rules abortion permissible only in extreme cases: specifically when a woman's “hard travail” places her life in unquestionable danger (Oholoth 7:6). This is a codification of Maimonides's concept of the rodef or “pursuer.” So, traditional Jewish law holds that the preborn child has a right to life equal to the mother's—except when he poses an imminent and actual danger to her life.
The Catholic parallel to the “hard travail” exception is called the “double effect.”
The chief justice of the Supreme Rabbinical Court of America and the U.S. coordinator of the Jewish Survival Legion, Rabbi Marvin Antelman, clearly stated the position of Jewish Noahide law on abortion in 1978 when he said, “All major religions have their parochial and their universal aspects, and the problem of abortion is not a parochial one. It is of universal morality and it is neither a Catholic problem, nor a Jewish problem, nor a Protestant problem. It involves the killing of a human being, an act forbidden by universal commandment.”
Chief rabbi of England Dr. Immanuel Jakabovits outlined the basis for the reasoning behind this statement when he explained, “Jewish law sees every human life as having the sanctity of intrinsic and infinite worth. One life has as much value as one hundred or one thousand; you cannot multiply infinity and you cannot divide it. So every human being has an identical worth and is identically worth saving.”
Source: The Facts of Life: An Authoritative Guide to Life and Family Issues, by Brian Clowes PhD (Human Life International, Front Royal, Va.). Reprinted with permission.