by Daniel Eisenberg, M.D.
Stem cell research is among the most promising and
controversial technological breakthroughs of our time. What is the halachic perspective on such research and
what could the possible objections to such research be?
- In Vitro Fertilization
- Abortion in Jewish Law
- Are Pre-Embryos Included in The Prohibition of Abortion?
- Forty Days
- May a Very Early Embryo be Sacrificed for Stem Cells?
- May We Fertilize Ova Specifically to Create an Embryo to be Sacrificed for Stem Cells?
- "Fences" Around the Law & Use of Stem Cells & Aborted Fetal Tissue
Most cells in
the human body are differentiated and, if they maintain the ability
to divide at all, have the ability to form only cells similar to themselves.
Stem cells have the unique property of being able to divide, while maintaining
their totipotent or pluripotent characteristics. Early in mammalian
development, stem cells (under the proper conditions) have the ability
to differentiate into every cell of the human body (totipotent), potentially
forming an entire fetus. Stem cells derived from later stages of mammalian
development have the ability to differentiate into multiple cell types,
but not into an entire organism. If we were able to manipulate the conditions
controlling cellular differentiation, we might be able to create replacement
cells and organs, potentially curing illnesses such as diabetes, Alzheimer's
disease, and Parkinson's disease.
The ultimate promise of stem cell technology would
be to combine it with cloning. Imagine a man dying of liver failure.
If we could take a somatic cell from his skin and place the nuclear
DNA into a denucleated egg cell, we would have created an almost exact
copy of that sick man's cell, capable of differentiating into his
clone. Instead of allowing the cloned cell to develop into a fetus,
we might place it (or its stem cells alone) into the appropriate environment
that would cause it to differentiate into a liver that would be virtually
genetically identical to the sick man. If we could "grow"
this liver to maturity, we could offer the sick man a liver transplant
without the risk of rejection and without the need for anti-rejection
This sounds like a virtual panacea for many of man's
ills. Yet we still do not know if we are able to successfully clone
a human, nor are we sure what practical value can be derived from stem
cells. We are currently in the realm of fascinating speculation. It
will require years of very expensive, labor intensive research to determine
the potential that stem cells hold for the treatment, palliation, and
cure of human illness. While stem cells have been isolated from adults
and aborted fetuses, the best source is the "pre-embryo,"
the small clump of cells that compose the early zygote only a few days
following conception. Therefore, to best investigate the latent possibilities
inherent in stem cells, scientists wish to use the approximately 100,000
"excess" frozen pre-embryos that are "left over"
from earlier IVF attempts.
There is little
argument that the use of stem cells derived from adult somatic tissue
pose few ethical problems. The issues raised by stem cell research involve
the use of in vitro fertilized eggs which have not yet been implanted
in a woman and the use of tissue from aborted fetuses.
The issues raised by stem cell research may be divided
into several questions that will be covered in this article.
In Vitro Fertilization
Artificial insemination has been dealt with a length
by a spectrum of poskim (rabbis qualified to decide matters of
Jewish law). While artificial insemination by a donor is generally strongly
condemned, the use of a husband's sperm for artificial insemination
in cases of necessity was accepted by most Rabbinical authorities.
The question of in vitro fertilization was dealt with later. A significant
majority of authorities accepted in vitro fertilization under the same
rubric and limitations as artificial insemination, including the
fulfillment of the mitzvah of procreation. However, a fundamentally
new question arose. What is the status of the "spare" embryos
that are not implanted as part of the first cycle of IVF? Must they
be implanted in the mother as part of another attempt at pregnancy.
May/must they be donated to another women to allow the pre-embryo its
chance at life? May they remain frozen indefinitely? Most importantly
to our topic, the question arose - may pre-embryos be destroyed? To
answer this question, we must first generally examine the Jewish approach
Abortion in Jewish Law
The traditional Jewish view of abortion does not fit conveniently into either of the major "camps"
in the current American abortion debate. We neither ban abortion completely,
nor do we allow indiscriminate abortion "on demand." To gain
a clear understanding of when abortion is sanctioned, or even required,
and when it is forbidden, requires an appreciation of certain nuances
of halacha (Jewish law) which govern the status of the fetus.
The easiest way to conceptualize a fetus in halacha
is to imagine it as a full-fledged human being - but not quite. In most
circumstances, the fetus is treated like any other "person."
Generally, one may not deliberately harm a fetus, and sanctions are
placed upon those who purposefully cause a woman to miscarry. However,
when its life comes into direct conflict with an already born person,
the autonomous person's life takes precedence.
It follows from this simple approach that, as a general
rule, abortion in Judaism is permitted only if there is a direct threat
to the life of the mother by carrying the fetus to term or through the
act of childbirth. In such a circumstance, the baby is considered tantamount
to a rodef, a pursuer after the mother with the intent to kill her.
Nevertheless, as explained in the Mishna (Oholos 7:6), if it would be
possible to save the mother by maiming the fetus, such as by amputating
a limb, abortion would be forbidden. Despite the classification of the
fetus as a pursuer, once the baby's head has been delivered, the baby's
life is considered equal to the mother's, and we may not choose one
life over another, because it is considered as though they are each
pursuing the other.
Judaism recognizes psychiatric as well as physical
factors in evaluating the potential threat that the fetus poses to the
mother. However, the danger posed by the fetus (whether physical or
emotional) must be both probable and substantial to justify abortion.
The degree of mental illness which must be present to justify termination
of a pregnancy is not well established and therefore criteria for permitting
abortion in such instances remain controversial.
As a rule, halacha does not assign relative values
to different lives. Therefore, almost all major poskim forbid abortion
in cases of abnormalities or deformities found in a fetus. Rabbi Moshe
Feinstein, one the greatest poskim in this century, rules that even
amniocentesis is forbidden if it is performed only to evaluate for birth
defects for which the parents might request an abortion. Nevertheless,
a test may be performed if a permitted action may result, such as performance
of amniocentesis or drawing alpha-fetoprotein levels for improved peripartum
or postpartum medical management. While most poskim forbid abortion
for "defective" fetuses, Rabbi Eliezar Waldenberg (in his
"Tzitz Eliezer," vol. 9, chapter 51:3) is a notable exception.
Rabbi Waldenberg allows first trimester abortion of a fetus which would
be born with a deformity that would cause it to suffer, and termination
of a fetus with a lethal fetal defect such as Tay Sachs up to the end
of the second trimester of gestation.
The question of abortion in cases of rape, incest,
and adultery is a complex one, with various legal justifications propounded
on both sides. In cases of rape and incest, a key issue would be the
emotional toll exacted from the mother in carrying the fetus to term.
The same analysis used in other cases of emotional harm might be applied
here. Cases of adultery interject additional considerations into the
debate which are beyond the scope of this short article.
In sum, the parameters determining the permissibility
of abortion within halacha are subtle and complex.
Are Pre-Embryos Included in The
Prohibition of Abortion?
While the practical aspects of the Jewish approach
to abortion are relatively agreed upon, the exact source and nature
of the prohibition is not. Depending on the origin of the prohibition,
the application to the pre-embryo will differ. For instance, while most
halachic authorities consider the prohibition of abortion to be from
the Torah, a few consider it to be Rabbinic in nature. It is interesting
to note that both the person who performs the abortion as well as the
woman who voluntarily allows it to be done are culpable.
The most obvious place to look for the Biblical prohibition
would be from the aseret ha'dibrot (Ten Commandments), "Thou shalt
not murder". This prohibition, called retzicha, usually carries
a death penalty for transgression. Nevertheless, it appears the Torah
itself teaches that killing a fetus is not equivalent to killing an
adult. The Torah specifically states that if in the course of an
altercation with a third party, a person causes a woman to miscarry,
he pays only monetary damages, while if the woman herself were to die
of her injuries, the aggressor would receive a death sentence. Rabbi
Yehuda Ashkenazi, in his commentary on the Code of Jewish Law, reasons
from here that a fetus is not a full-fledged person, since regarding
the one who hits the woman, causing her to miscarry, ". . . he
pays the value of the child and we do not label him a murderer, nor
do we execute him. . .."
Notwithstanding the statement of Rabbi Ashkenazi, several
poskim rule that abortion does represent murder, but without the punishment
of death. This law is similar to the law of one who kills a treife
(a specific type of terminally ill person), for whom there is a prohibition
of murder, but no death penalty. If the pre-embryo is included in
this prohibition, then very little short of the pre-embryo posing a
threat to someone's life could justify its destruction. An independent
threat to the life of a third party would not suffice to allow destroying
The argument regarding whether a fetus is included
in the prohibition of murder is complicated and fascinating. Both
positions garner support from two sides of the same page of the Talmud.
Arachin 7a states that the court should strike the abdomen of a pregnant
woman to cause a miscarriage prior to her execution. The life of
the fetus seems inconsequential in that discussion. On the other hand,
Arachin 7b states that the Sabbath may be desecrated for the life of
a fetus, something which may only be done to save a life, for pikuach
nefesh. This apparent contradiction is dealt with at length in the responsic
But is the pre-embryo included in this prohibition?
That question is best answered by evaluating the next possible Biblical
source for abortion. When Noah and his family exited the ark, G-d commanded
them seven laws, which apply to all of humanity. The usual translation
of one of these laws is: "Whoever sheds the blood of man, by man
shall his blood be shed." The Torah clearly demands capital
punishment for murder. While this prohibition appears straightforward,
there is a fascinating twist.
The Talmud attempts to prove that non-Jews, who
are not obligated by most of the Torah's commandments given at Mount
Sinai, are forbidden to perform abortions. The Talmud brings the
literal translation of the previously mentioned passage (with slightly
altered punctuation), which is: "Whoever sheds the blood of man,
within man, his blood shall be shed." It then asks: "What
is the meaning of 'man within man'? This can be said to refer to a fetus
in its mother's womb." This prohibition, as part of the Noachide
laws, would apply to all people, Jew and non-Jew alike, although for
technical reasons, the degree of severity would differ.
Once the "standard" prohibition of retzicha
(murder) is separated from that of killing a fetus, we may investigate
how this difference might affect the status of the pre-embryo. From
the Talmudic discussion of abortion, we might expect that pre-embryos
are not covered by the prohibition of abortion, because they have never
been implanted. The rationale for such a decision is based on the concept
that a pre-embryo left in its petri dish will die. It is not even potential
life until it is implanted in an environment in which it can mature.
Others derive the prohibition of abortion from the
Torah's proscription of inflicting damage to one's self or others (chavala).
One may not wound one's self without a valid reason (such a medical
necessity as in surgery). Obviously, one may not damage someone else.
As a result, some claim that the prohibition of abortion arises from
the prohibition of the woman wounding herself, while others feel
that the derivation is from the prohibition of wounding the fetus.
Unlike murder, for which only a threat to the mother's life could
justify killing the fetus, the rationale of chavala allows greater leeway
in allowing its abrogation. Particularly, if the wounding of the mother
is the prohibition, her consent to being wounded might be considered
a determining factor. Whether this prohibition applies to a pre-embryo
is open to debate (albeit my personal opinion is that the prohibition
of chavala does not apply at this level).
The last possible prohibition to consider is the Torah's
forbidding of "wasting seed" (hashchatat zera). This is
the main prohibition involved in questions of male contraception (for
example, condoms) as well as the laws governing gathering of sperm for
analysis, IVF, or artificial insemination. The prohibition forbids the
"useless" emission or destruction of sperm that could create
life. Some halachic authorities have ruled that excess sperm from fertility
treatments may be destroyed. Further, the emission of semen for analysis
has been permitted as part of the process of procreation in those suffering
from infertility. (Nevertheless, according to most poskim, this
prohibition does not apply once fertilization has occurred.) Since this
ban may be waived for the sake of saving a life, it is conceivable
that destroying a pre-embryo to save someone's life (or potentially
treat severe illness; this would bring us into the complicated question
of "v'chi omrim lo l'adam chatei bishvil sheyizke chaveirecha"
-- do we allow one to sin in order to save his friend, -- an issue beyond
the scope of this article) would be permitted as part of the mitzvah
of pikuach nefesh.
Two positive Biblical commandments bear on the obligation
to save life (the obligation of hatzala). The Torah requires that we
"Do not stand idly by as your neighbor's blood is being shed."
This mitzvah is interpreted by the Talmud to require one to expend
positive effort and even money to protect an endangered person. Maimonides
learns the whole commandment for a qualified individual to heal his
neighbor from the obligation to return lost objects. Regarding a lost
object, the Torah commands: ". . . and you should surely restore
it to him." From an extra letter in the sentence, Maimonides
derives that if one must return a lost object, he must certainly return
someone's "lost" health.
Both of these positive commandments may apply regardless
of whether there may be any prohibition of abortion for a pre-embryo.
But do these positive commandments apply to a pre-embryo? That is, do
we have a positive obligation to protect the pre-embryo that is sitting
in the freezer?
In our analysis, we must also evaluate whether we are
more lenient with the destruction of an embryo prior to forty days gestation.
There is reason to argue that prior to forty days gestation, the fetus
lacks "humanity." The Mishna states that a miscarriage
prior to forty days does not cause tumat leida. The daughter of
a Cohen (priest) whose non-Cohen husband has died may continue eating
trumah (tithes) only if she has no children and is not pregnant. Rav
Chisda states that in a case where her non-Cohen husband died soon
after marriage, she may continue eating trumah for forty days. He reasons
that if she is not pregnant, then there is no problem, and that if she
is pregnant, that up to forty days the fetus is "mayim b'alma (mere
These sources suggest that a fetus prior to forty days
gestation is not considered to be an actual person and we might extrapolate
that destruction of such a fetus is not forbidden by Jewish law. If
we now apply this reasoning to the possible sources for abortion discussed
above, we note consistency on the part of the poskim.
Rabbi Unterman, former Ashkenazi chief Rabbi of Israel,
who ruled that a fetus is protected by the prohibition of murder (retzicha),
rejects these sources as removing the early embryo from the prohibition
of murder. He bolsters his opinion by quoting from Toras Ha'Adam,
a famous Jewish law book by Nachmanides (Ramban) that discusses medical
issues. The Ramban quotes the Ba'al Halachot Gedolot, who asserts that
one may desecrate the Sabbath for a fetus because, by desecrating one
Sabbath, the fetus will be able to fulfill many Sabbaths in the future.
Thus, the Ba'al Halachot Gedolot argues that saving the life a fetus
before forty days overrides the Sabbath; therefore, argues Rabbi Unterman,
feticide is murder.
Rabbi Yair Bachrach, author of Chavot Yair, does not
accept the forty days distinction because he derives the prohibition
of feticide from wasting male seed, which is prohibited even before
Rabbi Yosef Trani (author of Responsa Maharit), who
argues that abortion is forbidden as chavala (wounding) of the mother,
does not specifically mention the forty day cutoff. However, Rabbi Yechiel
Weinberg (author of the Responsa Seridei Aish), clearly held that there
is no prohibition of abortion before forty days according to Rabbi Trani's
opinion since there is no "limb" to injure prior to formation
of a recognizable fetus at forty days. Rabbi Weinberg himself at
first permitted abortion prior to forty days, but later reconsidered
All of the above approaches apply only to Jews who
are bound by Torah law. The prohibition of abortion for non-Jews, as
discussed above, devolves from the Noachide laws. Of course, non-Jews
are forbidden to commit homicide. Yet, according to many commentators,
non-Jews are not bound by the commandment in Leviticus 19:16 to protect
the lives of their comrades, since it was not commanded to Noah. The
scope of their prohibition includes murder and "shedding blood
of man within man." These obligations include only actual lives,
not potential lives. Therefore, according to Rabbi Unterman, there
is no prohibition of abortion for a non-Jew, nor for a Jew to aid in
such an abortion, before the fortieth day of gestation.
May a Very Early Embryo be Sacrificed for Stem Cells?
Now that we have analyzed the possible ethical issues
in destroying pre-embryos, what is the final outcome? For non-Jews,
the issue appears most direct. The combination of the pre-embryo never
having existed within a uterus and the generally accepted leniency toward
abortion within the first forty days, would strongly argue for a permissive
ruling regarding the destruction of pre-embryos for stem cells.
Regarding Jews, the answer is more complicated. Since
stem cell research is a new endeavor and cloning of humans has not yet
occurred, there are no published responsa on the topic. We must, therefore,
look to more practical cases that encompass our question to find an
applicable ruling. We find such an issue with respect to the best course
of action for couples who wish to avoid having children with Tay Sachs
disease when both partners are carriers of the Tay Sachs gene. A similar
problem arises in families where the wife carries a gene for a sex-linked
disease, such as Fragile-X.
The most promising option for such couples is preimplantation
diagnosis, in which a zygote conceived in vitro has a few cells removed
to be tested for genetic defects before implantation. Only a zygote
that is not homozygous for Tay Sachs or not a male carrier of Fragile-X
would be implanted. Rabbi Yosef Shalom Eliyashuv, possibly the most
influention posek in Israel today, has permitted preimplantation diagnosis
and destruction of affected zygotes to prevent cases of Fragile-X and
even in a case of a woman with neurofibromatosis who only had skin lesions.
Rabbi Dovid Feinstein has taken a similar view as to the permissibility
of discarding "extra" pre-embryos. Pre-implantation diagnosis,
which is already accepted by some Rabbinic authorities, is likely to
be acceptable to most Jewish legal experts when used to prevent serious
diseases in offspring.
Based on these rulings, it would seem that we now have
a practical answer to our question of stem cell research. If the pre-embryo
may be destroyed, it certainly may be used for research purpose and
other life-saving work. In fact, Rabbi Moshe Dovid Tendler, in testimony
for the National Bioethics Advisory Commission, argued strongly
in favor of the use of pre-embryos for stem cell research. Nevertheless,
it is important to realize that this conclusion is not unanimous
and that all of these rulings are predicated upon the understanding
that the pre-embryo is not included in the prohibition of retzicha (murder).
May We Fertilize Ova Specifically to Create an Embryo to be Sacrificed for Stem Cells?
The creation of embryos for the purpose of taking their
stem cells is a complex issue. While no responsa yet exist specifically
dealing with this question, it is likely that Rabbinic authorities will
not favor such a leniency. The mere existence of already created pre-embryos
creates a need to decide the halachic ramifications of their destruction.
We therefore may decide that such research is permitted bedieved (ex
post facto), once the pre-embryos exist. However, since there are poskim
who forbid abortion even within the first forty days, it is much
harder to argue lichatchila (a priori) that creation of pre-embryos
with the intention of destroying them is permitted.
There are additional questions that we as a society
must ponder. May we and should we deliberately create pre-embryos in
order to destroy them?
"Fences" Around the Law & Use of Stem Cells & Aborted Fetal Tissue
The Rabbis often create protective edicts (gezerot)
to prevent the desecration of Torah law. Additionally, the Rabbis may
promulgate decrees intended to protect Torah values by preventing untoward
behavior that is not already prohibited by the Torah itself. For example,
more than 1000 years ago, Rabbenu Gershon enacted gezerot banning polygamy
and opening the mail of others, despite the absence of actual Torah
prohibitions for either of these two actions.
The protection of life is a strongly held Torah ideal.
While the destruction of pre-embryos in the course of fertility treatments
or to prevent disease may be permitted, this does not mean that pre-embryos
may be destroyed without compunction. To avoid the proverbial "slippery
slope," should we ban stem cell research on embryonic stem cells
as a dangerous encroachment on the sanctity of life? That is, even if
pre-embryos may be destroyed, should we enact preventative laws barring
stem cell research that requires the destruction of potential lives
to avoid cheapening life by treating the process of creating humans
as another scientific process, stripped of its miraculous underpinnings?
In his testimony, Rabbi Tendler summed up the issue of protective enactments
Jewish law consists of biblical and rabbinic legislation.
A good deal of rabbinic law consists of erecting fences to protect biblical
law. Surely our tradition respects the effort of the Vatican and fundamentalist
Christian faiths to erect fences that will protect the biblical prohibition
against abortion. But a fence that prevents the cure of fatal diseases
must not be erected, for then the loss is greater than the benefit.
In the Judeo-biblical legislative tradition, a fence that causes pain
and suffering is dismantled. Even biblical law is superseded by the
duty to save lives, except for the three cardinal sins of adultery,
idolatry, and murder. . . Life saving abortion is a categorical imperative
in Jewish biblical law. Mastery of nature for the benefit of those suffering
from vital organ failure is an obligation. Human embryonic stem cell
research holds that promise. . ..
Human embryonic germ cells may also be derived from
gamete ridge tissue removed from first trimester abortuses (at approximately
eight-weeks gestation). While abortion of fetuses is a grave offense,
it is difficult to justify prohibiting the use of life-saving tissue
from these aborted fetuses for fear of encouraging or condoning abortion.
This is another case where the cost of a preventative enactment might
be the avoidable death of human beings. 
Sources: Dr. Eisenberg resides with his
wife and children in Bala Cynwyd, Pa. This article was reviewed for
halachic accuracy by Rabbi Sholom Kaminetsky of the Talmudical Yeshiva
of Philadelphia. If you have any comments or questions about this article
or other medical / halachic issues, feel free to contact Dr. Eisenberg
 While the nuclear DNA would be identical to the donor skin cell, the
mitochondrial DNA would be that of the donor egg.
[2K] See "Artificial Insemination in Jewish Law," Maimonides: Health
in the Jewish World, Vol 5, No. 1, Winter, 1999.
 With the important exceptions of (1) Rabbi Ovadia Yosef, who forbids
it and rules that it does not fulfill the obligation of fathering children,
(2) Tzitz Eliezer XV, no. 45, and (3) Rabbi Moshe Sternbach who denies
paternity to the sperm donor and forbids the procedure.
 The use of sperm for IVF once the mitzvah of procreation has been fulfilled
is more controversial.
 See the article by Rabbi Yitzchok Breitowitz, "The Preembryo in
Halacha" posted on JLaw.com at http://www.JLaw.com/Articles/preemb.html
 The development of cryogenic techniques to freeze pre-embryos only pushed
off the crucial question of whether pre-embryos could be destroyed.
Prior to cryogenic techniques, several Rabbinic authorities ruled that
all fertilized embryos must be implanted. This severely limited the
availability of IVF to Torah observant Jews because of the great expense
and low yields of each IVF attempt (necessitating fertilization of many
ova), and the inherent risk of implanting many embryos. With the advent
of cryogenic techniques, many ova could be fertilized with only a few
implanted. Nevertheless, the question of disposition of these "frozen"
pre-embryos which now number approximately 100,000 remains.
 Nishmat Avraham, Orach Chaim 656:1 (p. 92)
 Exodus 20:13
 Exodus 21:22-23
 Be'er Hetiv, Choshen Mishpat 425:2
 See Rabbi I.Y. Unterman, Responsa Shevet M'Yehuda, Vol. I, p. 29 and
Noam 6 (1963): 1-11.
 A treife is a person with an organic illness that is expected to be
fatal within a year.
 See Igrot Moshe, Choshen Mishpat II, 69B
 For more extensive treatment of this debate, see Jewish Ethics and Halakhah
For Our Time, Sources and Commentary, Vol. I, by Rabbi Basil F. Herring.
 To spare her the embarrassment of bleeding during her execution.
 Genesis 9:6
 Sanhedrin 67b: "In the name of Rabbi Yishmael they said: A ben
Noach [is liable] even for killing a fetus. What is the reasoning of
Rabbi Yishmael? Because it is written [in Genesis 9:6]: 'Whoever sheds
the blood of man by man [literally "in man"], his blood shall
be shed'. What is the meaning of 'man in man'? This can be said to refer
to a fetus in its mother's womb."
 Since the Torah was given to the Jews at Mount Sinai, only they are
bound by its commands. Nevertheless, all laws given to Noah, the father
of all nations, are binding on non-Jews.
 Tosofot, Chullin 33a, (d.h. "Echad oveid kochavim"), Tosofot,
Sanhedrin 59a (d.h. "Layka")
 Bava Kamma 90b based on Genesis 9:5 ("the blood of your lives I
will surely require"). See Responsa Maharit 97 & 99. See also
Responsa Seridei Aish, vol. 3, no. 127 (originally published in Noam
 The laws of damage in halacha are extensively discussed in the Torah,
Talmud, and codes of Jewish law.
 See Responsa Seridei Aish, vol. 3, no. 127 (p. 249)
 Rabbi J. David Bleich, Contemporary Halakhic Problems, Vol. 1, p. 341
 As noted above, the fetus would be classified a rodef
 See Nida 13b and Responsa Chavot Yair, no. 31. Responsa Sheilot Yaavetz,
no. 43 argues that once the sperm has been deposited in the woman, the
primary prohibition of hashchatas zera no longer applies.
 Igrot Moshe Even HaEzer I:70, III:14
 Generally, all Torah prohibitions except for murder, idolatry, and forbidden
sexual relationships are waived to save a human life.
 Leviticus 19:16
 Sanhedrin 73a
 Deuteronomy 22:1-2
 Maimonides, Commentary on the Mishnah, Nedarim 4:4
 Nidda 30a
 Tumat leida is the impurity that is created by the birth process, whether
live or by miscarriage.
 Yevamot 69b
 Torat HaAdam (in Mosad HaRav Kook Kitvei Haramban, Vol. 2, p. 29)
 This line of reasoning is brought in Talmud Yoma 85b as one possible
reason for why saving a life overrides the Sabbath.
 See Responsa Sheilot Yaavetz, no. 43, where Rabbi Yaakov Emden argues
that "wasting seed" only bars preventing the semen from reaching
the woman's uterus. He nevertheless forbids abortion prior to forty
days for other reasons.
 Seridei Aish, vol. 3:350, n.7
 Seridei Aish, vol. 3, no. 127 (p. 249)
 Responsa Shevet M'Yehuda, Vol. I, 9 and Noam 6:4.
 Rabbi Chaim Ozer Grodzinski (Responsa Achiezer, III, 65:14) even entertains
the possibility that there may be no Biblical prohibition of abortion
before forty days. See also: Tzofnat Paneach 59; Responsa Bet Shlomah,
Choshen Mishpat 162; Torat Chesed, Even Ha'ezer, 42:33 all of whom discuss
the decreased stringency of abortion within the first forty days.
 Males with a single gene for a sex-linked disease will be affected by
 Personal correspondance with Dr. Avraham Steinberg.
 Personal correspondance with Rabbi Sholom Kamenetsky.
 Stem Cell Research and Therapy: A Judeo-Biblical Perspective, Ethical
Issues in Human Stem Cell Research, Volume III: Religious Perspectives,
September 1999, pp.H-3 to H-5. The full text may be downloaded from
the National Bioethics Advisory Commission website at http://bioethics.gov/pubs.html.
 "The Judeo-biblical tradition does not grant moral status to an
embryo before forty days of gestation. Such an embryo has the same moral
status as male and female gametes, and its destruction prior to implantation
is of the same moral import as the 'wasting of human seed.' After forty
days-the time of 'quickening' recognized in common law-the implanted
embryo is considered to have humanhood, and its destruction is considered
an act of homicide. Thus, there are two prerequisites for the moral
status of the embryo as a human being: implantation and forty days of
gestational development. The proposition that humanhood begins at zygote
formation, even in vitro, is without basis in biblical moral theology."
Testimony of Rabbi Moshe Dovid Tendler, Ph.D , Stem Cell Research and
Therapy: A Judeo-Biblical Perspective, Ethical Issues in Human Stem
Cell Research, Volume III: Religious Perspectives, September 1999, p.H-3.
 E.g., Rabbi J. David Bleich has voiced opposition to the destruction
of pre-embryos and their use in stem cell research.
 Responsa Seridei Aish, vol. 3:350, n.7, Responsa Shevet M'Yehuda, 1;50,
Responsa Maharash Engel, 7:85, and Rabbi Moshe Yonah Zweig, Noam 7:48.
 "In stem cell research and therapy, the moral obligation to save
human life, the paramount ethical principle in biblical law, supersedes
any concern for lowering the barrier to abortion by making the sin less
heinous. Likewise, the expressed concern that this research facilitates
human cloning is without merit. First, no reputable research facility
is interested in cloning a human, which is not even a distant goal,
despite the pluripotency of stem cells. Second, those on the leading
edge of stem cell research know that the greater contribution to human
welfare will come from replacement of damaged cells and organs by fresh
stem cell products, not from cloning. Financial reward and acclaim from
the scientific community will come from such therapeutic successes,
not from cloning." Testimony of Rabbi Moshe Dovid Tendler, Ph.D.,
Stem Cell Research and Therapy: A Judeo-Biblical Perspective Ethical
Issues in Human Stem Cell Research, Volume III: Religious Perspectives,
September 1999, p.H-4.
 Other issues applicable to stem cell research are generic and apply
equally to all research. Full informed consent, careful risk-benefit
analysis, allocation of scarce resources, and the role of financial
gain and renumeration in research have all been dealt with in Jewish
law, and are beyond the scope of this article.