asked the following question: A married woman confessed to adultery, and, finding herself pregnant, asked for an abortion. Bachrach was asked whether it is permissible by Jewish law to do so. He discusses most of the material that [ have mentioned above, and at first says that it would seem that a fetus is not really a nefesh and it might be permitted to destroy it, except that this would encourage immorality. But he continues, from the discussion of the Tosafot in Hulin, that a Jew is not permitted(even though he would not be convicted) to destroy a fetus, that it is forbidden for him to do so.
Yet in the next century the opposite opinion is voiced, and also by a great authority, namely Jacob Emden (Yaavetz 1, 43). He is asked concerning a pregnant adulteress whether she may have an abortion. He decides affirmatively, on the rather curious ground that if we were still under our Sanhedrin and could inflict capital punishment, such a woman would be condemned to death and her child would die with her anyhow. Then he adds boldly(though with some misgivings) that perhaps we may destroy a fetus even to save a mother excessive physical pain.
A much more thorough affirmative opinion is given by Ben Zion Uziel , the late Sephardic Chief Rabbi (in Mishpetei Uziel 111, 46 and 47). He concludes, after a general analysis of the subject, that an unborn fetus is actually not a nefesh at all and has no independent life. It is part of its mother, and just as a person may sacrifice a limb to be cured of a worse sickness, so may this fetus be destroyed for the mother's benefit. Of course, he reckons with the statement of the Tosafot in Hulin 33a that a Jew is not permitted(lo shari) to destroy a fetus, although such an act is not to be considered murder. Uziel says that, of course, one may not destroy it. One may not destroy anything without purpose. But if there is a worthwhile purpose, it may be done. The specific case before him concerned a woman who was threatened with permanent deafness if she went through with the pregnancy. Uziel decides that since the fetus is not an independent nefesh but is only part of the mother, there is no sin in destroying it for her sake.