Wikipedia

Beginning of pregnancy controversy

Controversy over the beginning of pregnancy occurs in different contexts, particularly as it is discussed within the debate of abortion in the United States. Because an abortion is defined as ending an established pregnancy, rather than as destroying a fertilized egg, depending on when pregnancy is considered to begin, some methods of birth control as well as some methods of infertility treatment might be classified as causing abortions.

The viewpoint that pregnancy, or at least morally significant human life, begins at the exact moment that sperm and egg interact is highly controversial, although it is commonly held by groups such as the Roman Catholic Church and many traditionally religious individuals, and other alternate viewpoints are put forth.[1]

The controversy is not primarily a scientific issue, since knowledge of human reproduction and development has become very refined; the linguistic questions remain debated for other reasons. The issue poses larger social, legal, medical, religious, philosophical, and political ramifications because some people, such as Concerned Women for America, identify the beginning of a pregnancy as the beginning of an individual human being's life.[1] Many of these arguments are related to the anti-abortion movement. In this way of thinking, if the pregnancy has not yet begun, then stopping the process is not abortion and therefore can contain none of the moral issues associated with abortion, but if it is a pregnancy, then stopping it is a morally significant act.

A major complication is that ideological and religious concepts such as "ensoulment" (whether or not a human being is said to have gone from mere matter to having a spiritual entity inside) and "personhood" (whether or not a human being is said to be a distinct individual with innate human rights versus otherwise) exist outside of scientific analysis, and thus many individuals have argued that the beginning of pregnancy cannot be determined strictly through physical evidence alone. No experiment exists (or can exist) to measure the spirituality of an object or living thing in the same way that height, temperature, weight, etc. can be studied.

Generally speaking, some ideological and religious commentaries have argued that pregnancy should be stated as beginning at the first, exact moment of conception in which a human sperm makes full contact with an egg cell. In contrast, other commentaries have argued that the duration of pregnancy begins at some other point, such as when the fertilization process ends (when a new, independent cell genetically distinct from the prior egg and sperm exists) or when implantation occurs (when the new set of cells lodges itself against the uterine wall, allowing it to grow rapidly). The ambiguity's implications mean that, despite the scientific community being able to describe the physical processes in detail, the decision about what should be called "abortion" and what should be called "contraception" or pregnancy prevention are not agreed upon.[1]

Definitions of pregnancy beginning

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Traditionally, doctors have measured pregnancy from a number of convenient points, including the day of last menstruation, ovulation, fertilization, implantation and chemical detection.[2] This has led to some confusion about the precise length of human pregnancy, as each measuring point yields a different figure.

Comparison of dating systems for a typical pregnancy
Event Gestational age

(from the start of the last menstrual period)

Fertilization age Implantation age
Menstrual period begins Day 1 of pregnancy Not pregnant Not pregnant
Has sex and ovulates 2 weeks pregnant Not pregnant Not pregnant
Fertilization; cleavage stage begins[3] Day 15[3] Day 1[3][4] Not pregnant
Implantation of blastocyst begins Day 20 Day 6[3][4] Day 0
Implantation finished Day 26 Day 12[3][4] Day 6 (or Day 0)
Embryo stage begins; first missed period 4 weeks Day 15[3] Day 9
Primitive heart function can be detected 5 weeks, 5 days[3] Day 26[3] Day 20
Fetal stage begins 10 weeks, 1 day[3] 8 weeks, 1 day[3] 7 weeks, 2 days
First trimester ends 13 weeks 11 weeks 10 weeks
Second trimester ends 26 weeks 24 weeks 23 weeks
Childbirth 39–40 weeks 37–38 weeks[4]: 108  36–37 weeks

At its 2004 Annual Meeting, The American Medical Association passed a resolution in favor of making "Plan B" emergency contraception available over-the-counter, and one of the claims in the resolution was that hormonal contraception that may affect implantation "cannot terminate an established pregnancy."[5] Similarly, the British Medical Association has defined an "established pregnancy" as beginning at implantation.[6] The legal definition in the United Kingdom is not clear.[7]

Other definitions exist. The American Heritage Stedman's Medical Dictionary defines "pregnancy" as "from conception until birth."[8] Definitions like this may add to a lay person's confusion, as "conception" in a scientific context may be defined as fertilization,[9][10] in a medical context can mean either fertilization[11][12] or implantation[13] but in lay terms may mean both.[14]

Whether conception refers to fertilization or implantation would seemingly even impact "established pregnancies" such as an ectopic pregnancy. If conception is defined as at implantation, ectopic pregnancies could not be called pregnancies. However, some medical professionals who oppose birth control,[15] such as Walter Larimore of the Focus on the Family group, have argued that the medical definition of conception should include fertilization.[16]

Finally, the standard historical method of counting the duration of pregnancy begins from the last menstruation and this remains common with doctors, hospitals, and medical companies.[17] This system is convenient because it is easy to determine when the last menstrual period was, while both fertilization and implantation occur out of sight. An interesting consequence is that the dating of pregnancy measured this way begins two weeks before ovulation.

Although many anti-abortion advocates have argued that both pregnancy and status of a separate human life beginning happen at fertilization, several examples also exist of people within those movements taking alternate views. For example, doctor and social activist Bernard Nathanson wrote in his 1979 work Aborting America that a confirmed moment of implantation should be considered the point at which a distinct human being exists. He specifically stated (note that 'alpha' is his shorthand for an organized group of cells), "Biochemically, this is when alpha announces its presence as part of the human community by means of its hormonal messages, which we now have the technology to receive... know[ing] biochemically that it is an independent organism distinct from the mother."[18]

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In August 2008, the U.S. Department of Health and Human Services proposed a regulation to protect certain actions of health workers: refusal to provide patient services that the health workers believe to be abortifacient. The ban on discrimination against these employees would apply to all organizations that receive grant money from HHS. A draft version leaked in July proposed that the U.S. federal government define abortion as including "termination of [human] life... before... implantation." The official proposal dropped the definition of abortion, instead leaving it to the objecting individual to define abortion for him- or herself. Groups on both sides of the controversy believe the ban is intended to allow health workers to refuse to dispense IUDs and hormonal contraceptives, including emergency contraception. It has drawn widespread criticism from major medical and health groups.[19][20][21]

History

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In the past, pregnancy has been defined in terms of conception. For example, Webster's Dictionary defined "pregnant" (or "pregnancy") as "having conceived" (or "the state of a female who has conceived"), in its 1828 and 1913 editions.[22] However, in the absence of an accurate understanding of human development, early notions about the timing and process of conception were often vague.

Both the 1828 and 1913 editions of Webster's Dictionary said that to "conceive" meant "to receive into the womb and ... begin the formation of the embryo."[22] However most references say that it was only in 1875 that Oskar Hertwig discovered that fertilization includes the penetration of a spermatozoon into an ovum. Thus, the term "conception" was in use long before the details of fertilization were discovered. By 1966, a more precise meaning of the word "conception" could be found in common-use dictionaries: the formation of a viable zygote.[23]

In 1959, Dr. Bent Boving suggested that the word "conception" should be associated with the process of implantation instead of fertilization.[24] Some thought was given to possible societal consequences, as evidenced by Boving's statement that "the social advantage of being considered to prevent conception rather than to destroy an established pregnancy could depend on something so simple as a prudent habit of speech." In 1965, the American College of Obstetricians and Gynecologists (ACOG) adopted Boving's definition: "conception is the implantation of a fertilized ovum."[25]

The 1965 ACOG definition was imprecise because, by the time it implants, the embryo is called a blastocyst,[26] so it was clarified in 1972 to "Conception is the implantation of the blastocyst."[27] Some dictionaries continue to use the definition of conception as the formation of a viable zygote.[28]

Birth control – mechanism of action

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See also: Combined oral contraceptive pill § Mechanism of action

Birth control methods usually prevent fertilization.[29] This cannot be seen as abortifacient[30] because, by any of the above definitions, pregnancy has not started.[31] However, emergency contraception might have a secondary effect of preventing implantation, thus allowing the embryo to die.[32][33][34] Those who define pregnancy from fertilization subsequently may conclude that the agents should be considered abortifacients.[35]

Speculation about post-fertilization mechanisms is widespread, even appearing on patient information inserts for hormonal contraception, but there is no clinical support. One small study, using fourteen women, might be considered as providing evidence of such an effect for IUDs[36] and a study of the combined oral contraceptive pill has been proposed.[37]

Possibly affected methods

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  • Hormonal contraception, including emergency contraception, are known to be effective at preventing ovulation. Some scientists believe hormonal methods may have a secondary effect of interfering with implantation of embryos.[citation needed]
  • Intrauterine devices (IUDs) have been proven to have strong spermicidal and ovicidal effects;[38][39] the current medical consensus is that this is the only way in which they work.[40] Still, a few physicians have suggested they may have a secondary effect of interfering with the development of pre-implanted embryos;[36] this secondary effect is considered more plausible when the IUD is used as emergency contraception.[41]
  • The lactational amenorrhea method works primarily by preventing ovulation, but is also known to cause luteal phase defect (LPD). LPD is believed to interfere with the implantation of embryos.[42]
  • Natural Family Planning (NFP) methods are intended to prevent fertilization through avoiding intercourse during fertile periods. Luc Bovens argues that, under an assumption that the age of gametes has an effect on embryo viability, errors in NFP method result in the occurrence of lower-viability embryos. This is intended to be an ethical thought experiment; Bovens states that his assumption "is not backed up by empirical evidence, but does have a certain plausibility."[43] His argument is controversial.[44] The age of gametes at the time of fertilization has been shown to have no effect on miscarriage rates in most cases, but is a significant risk factor where there is history of miscarriage.[45] Age of gametes at the time of fertilization has been shown to have no effect on low birth weight or preterm delivery.[46]

Viability and established pregnancy

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A related issue that comes up in this debate is how often fertilization leads to an established, viable pregnancy.[citation needed] Research in in-vitro fertilization patients suggests that fertilized embryos fail to implant some 30% to 70% of the time, although it is unknown whether this rate corresponds to inherently low human implantation rates (in natural conception) or to an altered physiological state.[47][48] Of those that do implant, about 25% suffer early pregnancy loss by the sixth week LMP (after the woman's Last Menstrual Period), and an additional 7% miscarry or are stillborn.[49] As a result, even without the use of birth control, between 50% and 70% of zygotes never result in established pregnancies, much less birth.

Ethics of preventing implantation

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The intention of a woman to prevent pregnancy is an important factor in whether or not the act of contraception is seen as abortive by some anti-abortion groups. Hormonal contraceptives have a possible effect of preventing implantation of a blastocyst, as discussed previously. Use of these drugs with the intention of preventing pregnancy is seen by some anti-abortion groups as immoral. This is because of the possibility of causing the end of a new human life.[50]

However, hormonal contraception can also be used as a treatment for various medical conditions. When implantation prevention is unintentionally caused as a side effect of medical treatment, such anti-abortion groups do not consider the practice to be immoral, citing the bioethical principle of double effect.[51] Likewise, when a hormonal contraceptive is used with the intention of preventing fertilisation, the intended reduction in implantation failures, miscarriages and deaths from childbearing may outweigh the possibility that the method might cause some implantation failures.[citation needed]

A related application of the principle of double effect is breastfeeding. Breastfeeding greatly suppresses ovulation, but eventually an ovum is released. Luteal phase defect, caused by breastfeeding, makes the uterine lining hostile to implantation and as such may prevent implantation after fertilization.[42] Some pro-choice groups have expressed concern that the movement to recognize hormonal contraceptives as abortifacient will also cause breastfeeding to be considered an abortion method.[52][53]

Detectable pregnancy

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A protein called early pregnancy factor (EPF) is detectable in a woman's blood within 48 hours of ovulation if fertilization has occurred. However, testing for EPF is time-consuming and expensive; most early pregnancy tests detect human chorionic gonadotropin (hCG), a hormone that is not secreted until after implantation. Defining pregnancy as beginning at implantation thus makes pregnancy a condition that can be easily tested.[citation needed]

Philosophical issues

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The distinction in ethical value between existing persons and potential future persons has been questioned.[54] Subsequently, it has been argued that contraception and even the decision not to procreate at all could be regarded as immoral on a similar basis as abortion.[55] In this sense, beginning of pregnancy may not necessarily be equated with where it is ethically right or wrong to assist or intervene.[citation needed] In a consequentialistic point of view, an assisting or intervening action may be regarded as basically equivalent whether it is performed before, during or after the creation of a human being, because the result would basically be the same, that is, the existence or non-existence of that human being.[citation needed]

See also

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Notes

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  1. ^ a b c "The Implications of Defining When a Woman Is Pregnant". The Guttmacher Report on Public Policy. May 2005, Volume 8, Number 2.
  2. ^ Betz, Danielle; Fane, Kathleen (2024), "Human Chorionic Gonadotropin", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 30422545, retrieved 10 October 2024
  3. ^ a b c d e f g h i j Nair, Manju; Kumar, Bidyut (7 April 2016). "Embryology for fetal medicine". In Kumar, Bidyut; Alfirevic, Zarko (eds.). Fetal Medicine. Cambridge University Press. pp. 54–59. ISBN 978-1-107-06434-8.
  4. ^ a b c d Mishra, Sabita, ed. (7 August 2019). Langman's Medical Embryology. Wolters kluwer india Pvt Ltd. p. 48. ISBN 978-93-88696-53-1.
  5. ^ FDA Rejection of Over-The-Counter Status for Emergency Contraception Pills American Medical Association House of Delegates Resolution:443. Retrieved April 30, 2007
  6. ^ BMA (May 2005). "Abortion time limits: A briefing paper from the British Medical Association". Archived from the original on 27 August 2006. Retrieved 31 July 2006. "The term 'abortion' is used throughout this paper to refer to the induced termination of an established pregnancy (i.e. after implantation)."
  7. ^ Hope, T. & Savulsecu, J. "Handout 3: Outline of Legal Positions in England and Wales". Medical Ethics and Law Teaching Materials: Termination of Pregnancy. The Oxford Centre for Ethics and Communication in Health Care Practice, Oxford University. pp. Appendix 3: Some key points in the law on abortion and fetal damage. Archived from the original on 23 March 2006. – "It is generally assumed that when the Act states that 'pregnancy has not exceeded its 24th week' it means 24 weeks since the first day of the woman's last period. But this is not clear – particularly if there is evidence that conception had taken place on a day after this....The Attorney General said, in 1983 (see Brazier 1992 page 293-4) that there is no pregnancy until implantation. This is persuasive but not binding precedence." "Termination of Pregnancy Handout (pdf)" (PDF).
  8. ^ The American Heritage Stedman's Medical Dictionary, 2002
  9. ^ Hellweg, Paul (2011). The American Heritage Science Dictionary. Houghton Mifflin Harcourt Publishing Company. p. 137. ISBN 9780547470924. Archived from the original on 22 June 2013. Retrieved 6 October 2013.
  10. ^ Martin, Elizabeth A. (2012). A Dictionary of Science. Oxford University Press. p. 185. ISBN 978-0199561469.
  11. ^ Mosby (2012). Mosby's Medical Dictionary. Elsevier Health Sciences. p. 415. ISBN 978-0323085410.
  12. ^ Dorland (2011). Dorland's Illustrated Medical Dictionary. Saunders. p. 355. ISBN 978-1416062578.
  13. ^ "Sex Selection" (PDF). ACOG. February 2007. Archived from the original (PDF) on 10 June 2015.
  14. ^ "Conception". Merriam-Webster. 5 February 2024.
  15. ^ Larimore, Walter. "Ethical Issues Regarding Hormonal Contraceptives". The Truth About Birth Control. Retrieved 14 March 2011.
  16. ^ Larimore, Walter L; et al. (2004). "Response: Does Pregnancy Begin at Fertilization?" (PDF). Family Medicine.
  17. ^ Doctor:George P. Pettit, M.D. (2002). "Due Date Calculator".
    Hospital:Northwestern Memorial Hospital (2006). "What is a trimester?". Archived from the original on 4 November 2005.
    Medical company:The Merck Manuals Online Medical Library (2003). "Stages of Development: Pregnancy".
  18. ^ Nathanson, Bernard N.; Ostling, Richard N. (1979). Aborting America. Life Cycle Books. p. 216. ISBN 9780919225008.
  19. ^ Stein, Rob (31 July 2008). "Workers' Religious Freedom vs. Patients' Rights". Washington Post. pp. A01. Retrieved 5 August 2008.
  20. ^ Shapiro, Joseph (22 August 2008). "HHS Backs Protections For Anti-Abortion Doctors". Washington Post. Retrieved 24 August 2008.
  21. ^ Stein, Rob (22 August 2008). "Protections Set for Antiabortion Health Workers". Washington Post. pp. A01. Retrieved 24 August 2008.
  22. ^ a b Webster’s Revised Unabridged Dictionary Archived 2012-07-10 at archive.today (1913 and 1828) via the ARTFL Project. See definitions of "pregnant" and "pregnancy".
  23. ^ Webster’s Third New International Dictionary (1966), defining conception as the "act of becoming pregnant (formation of a viable zygote); state of being conceived; that which is conceived (embryo, fetus)..." quoted in Mallett Shelley, Conceiving Cultures Archived 2006-08-30 at the Wayback Machine, p. 284 (U. Mich. 2003).
  24. ^ Boving, B.G., "Implantation Mechanisms", in Mechanics Concerned With Conception. Hartman, C.G., ed. (Pergamon Press 1963), page 386.
  25. ^ American College of Obstetricians and Gynecologists Terminology Bulletin. Terms Used in Reference to the Fetus. No. 1. Philadelphia: Davis, September, 1965.
  26. ^ Biggers, J., "Ambiguity of the Word Conception: Implications if S. 158 is Enacted", The Human Life Bill Appendix, Hearings Before the Subcommittee on Separation of Powers of the Committee on the Judiciary, United States Senate, p. 281-288 (1982).
  27. ^ Hughes, E.C. "Gametogenesis and Fertilization", in Obstretric-Gynecologic Terminology. Philadelphia: Davis, 1972: 299–304.
  28. ^ Dictionary.com.
  29. ^ "Birth Control Options". my.clevelandclinic.org. Cleveland Clinic. Retrieved 14 July 2023.
  30. ^ Glasier, Anna (9 October 1997). "Emergency Postcoital Contraception". New England Journal of Medicine. 337 (15): 1058–1064. doi:10.1056/NEJM199710093371507. PMID 9321535. Any device or drug that acts after implantation is conventionally regarded as an abortifacient rather than a contraceptive.
  31. ^ Attia (12 May 2023). "Do I Need Emergency Contraception or the Abortion Pill?". plannedparenthood.org. Retrieved 14 July 2023.
  32. ^ Kahlenborn, Chris (2002). "Postfertilization Effect of Hormonal Emergency Contraception". Annals of Pharmacotherapy. 36 (3): 465–470. doi:10.1345/aph.1A344. PMID 11895061. S2CID 36847373.
  33. ^ Mozzanega, Bruno (2011). "How do levonorgestrel-only emergency contraceptive pills prevent pregnancy? Some considerations". Gynecological Endocrinology. 27 (6): 439–442. doi:10.3109/09513590.2010.501885. PMID 20670097. S2CID 6431709.
  34. ^ Rebecca Peck; Walter Rella; Julio Tudela; Justo Aznar; Bruno Mozzanega (February 2016). "Does levonorgestrel emergency contraceptive have a post-fertilization effect? A review of its mechanism of action". Linacre Q. 83 (1): 35–51. doi:10.1179/2050854915Y.0000000011. PMC 5102184. PMID 27833181. Plan B is the most widely used emergency contraceptive available. It is important for patients and physicians to clearly understand the drug's mechanism of action (MOA)... data suggest that when administered pre-ovulation, it may have a post-fertilization MOA.
  35. ^ DeSanctis, Alexandra (4 November 2016). "Yes, Some Contraceptives Are Abortifacients". nationalreview.com. National Review.
  36. ^ a b Stanford J, Mikolajczyk R (2002). "Mechanisms of action of intrauterine devices: update and estimation of postfertilization effects". Am J Obstet Gynecol. 187 (6): 1699–708. doi:10.1067/mob.2002.128091. PMID 12501086., which cites:
    Smart Y, Fraser I, Clancy R, Roberts T, Cripps A (1982). "Early pregnancy factor as a monitor for fertilization in women wearing intrauterine devices". Fertil Steril. 37 (2): 201–4. doi:10.1016/S0015-0282(16)46039-5. PMID 6174375.
  37. ^ Lloyd J DuPlantis, Jr (2001). "Early Pregnancy Factor". Pharmacists for Life, Intl. Retrieved 1 January 2007. {{cite journal}}: Cite journal requires |journal= (help)
  38. ^ "Mechanisms of the Contraceptive Action of Hormonal Methods and Intrauterine Devices (IUDs)". Family Health International. 2006. Archived from the original on 17 June 2006. Retrieved 5 July 2006.
  39. ^ Keller, Sarah (Winter 1996). "IUDs Block Fertilization". Network. Family Health International. Archived from the original on 23 June 2006. Retrieved 5 July 2006.
  40. ^ Grimes, David (2007). "Intrauterine Devices (IUDs)". In Hatcher, Robert A.; et al. (eds.). Contraceptive Technology (19th rev. ed.). New York: Ardent Media. p. 120. ISBN 978-0-9664902-0-6.
  41. ^ Trussell, James; Elizabeth G. Raymond (September 2010). "Emergency Contraception: A Last Chance to Prevent Unintended Pregnancy" (PDF). The Office of Population Research at Princeton University and the Association of Reproductive Health Professionals. Archived (PDF) from the original on 23 September 2010. Retrieved 27 October 2010. {{cite journal}}: Cite journal requires |journal= (help)
  42. ^ a b Díaz S, Cárdenas H, Brandeis A, Miranda P, Salvatierra A, Croxatto H (1992). "Relative contributions of anovulation and luteal phase defect to the reduced pregnancy rate of breastfeeding women". Fertil Steril. 58 (3): 498–503. doi:10.1016/S0015-0282(16)55251-0. PMID 1521642.
  43. ^ Luc Bovens (2006). "The rhythm method and embryonic death". Journal of Medical Ethics. 32 (6): 355–356. doi:10.1136/jme.2005.013920. PMC 2563373. PMID 16731736.
  44. ^ Bovens, L. (2006). "The rhythm method and embryonic death". Journal of Medical Ethics. 32 (6): 355–356. doi:10.1136/jme.2005.013920. PMC 2563373. PMID 16731736. Retrieved 10 July 2013.
  45. ^ Gray RH, Simpson JL, Kambic RT (May 1995). "Timing of conception and the risk of spontaneous abortion among pregnancies occurring during the use of natural family planning". American Journal of Obstetrics and Gynecology. 172 (5): 1567–1572. doi:10.1016/0002-9378(95)90498-0. PMID 7755073.
  46. ^ Barbato M, Bitto A, Gray RH, et al. (June–September 1997). "Effects of timing of conception on birth weight and preterm delivery of natural family planning users". Advances in Contraception. 13 (2–3): 215–228. doi:10.1023/A:1006508106197. PMID 9288339. S2CID 24939823.
  47. ^ Kennedy, T.G. Physiology of implantation. 10th World Congress on in vitro fertilization and assisted reproduction. Vancouver, Canada, 24–28 May 1997.
  48. ^ Smart Y, Fraser I, Roberts T, Clancy R, Cripps A (1982). "Fertilization and early pregnancy loss in healthy women attempting conception". Clin Reprod Fertil. 1 (3): 177–84. PMID 6196101.
  49. ^ Wilcox AJ, Baird DD, Weinberg CR (June 1999). "Time of implantation of the conceptus and loss of pregnancy". The New England Journal of Medicine. 340 (23): 1796–9. doi:10.1056/NEJM199906103402304. PMID 10362823.
  50. ^ Finn, J.T. (23 April 2005). ""Birth Control" Pills cause early Abortions". Pro-Life America — Facts on Abortion. prolife.com. Archived from the original on 19 August 2006. Retrieved 25 August 2006.
  51. ^ Doesn't breastfeeding do the same thing as the Pill? Archived 2006-10-15 at the Wayback Machine Eternal Perspective Ministries, 2006. Accessed May 2006.
  52. ^ "Emergency Contraception & Conscience: Christian Right Attacks on Contraceptives". About.com Religion & Spirituality Agnosticism / Atheism. Archived from the original on 28 June 2006. Retrieved 22 June 2006.
  53. ^ Shorto, Russell (7 May 2006). "Contra-Contraception". New York Times Magazine. pp. 4 of 9-page online article.
  54. ^ Page 212 and 213 in: Abortion and the Golden Rule By R. M. Hare. Philosophy and Public Affairs. Vol. 4, No. 3 (Spring, 1975), pp. 201-222 [1]
  55. ^ Do Potential People Have Moral Rights? By Mary Anne Warren. Canadian Journal of Philosophy. Vol. 7, No. 2 (Jun., 1977), pp. 275-289 [2]
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