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Controversy over the beginning of pregnancy usually occurs in the context of the abortion debate. Depending on where pregnancy is considered to begin, some methods of birth control or infertility treatment might be considered abortifacient. The controversy is not primarily a scientific issue since knowledge of human reproduction and development has become very refined, but rather is primarily a linguistic and definitional question. The issue may also have social, medical, political and legal ramifications, but only if one equates the "beginning of pregnancy" with the "beginning of an individual human being's life".


Definitions of pregnancy beginning

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

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."[1]

Similarly, the British Medical Association has defined an "established pregnancy" as beginning at implantation.[2] The legal definition in the United Kingdom is not clear.[3] Other definitions exist. The American Heritage Stedman's Medical Dictionary defines "pregnancy" as "from conception until birth."[4] There has been some debate on the matter of definition in medical journals.[5]

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.[6] 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.

Legal implications

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.[7][8][9]


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.[10] 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."[10] 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.[11]

In 1959, Dr. Bent Boving suggested that the word "conception" should be associated with the process of implantation instead of fertilization.[12] 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."[13]

The 1965 ACOG definition was imprecise because, by the time it implants, the zygote is called a blastocyst,[14] so it was clarified in 1972 to "Conception is the implantation of the blastocyst."[15] Some dictionaries continue to use the definition of conception as the formation of a viable zygote.[16]

Birth control - mechanism of action

See also COCP: Mechanism of Action

Birth control methods usually prevent fertilization. This cannot be seen as abortifacient because, by any of the above definitions, pregnancy has not started. However, some methods might have a secondary effect of preventing implantation, thus allowing the zygote to die. Those who define pregnancy from fertilization subsequently may conclude that the agents should be considered abortifacients.

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[17] and a study of the combined oral contraceptive pill has been proposed.[18]

Possibly affected methods

  • 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.
  • Intrauterine devices have been proven to have strong spermicidal and ovicidal effects;[19][20] the current medical consensus is that this is the only way in which they work.[21] Still, a few physicians have suggested they may have a secondary effect of interfering with the development of pre-implanted embryos;[22] this secondary effect is considered more plausible when the IUD is used as emergency contraception.[23]
  • 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.[24]
  • Fertility awareness methods are known to work by preventing fertilization. It has been speculated they have a secondary effect of creating embryos incapable of implanting (due to aged gametes at the time of fertilization),[25] although age of gametes at the time of fertilization has been shown to have no effect on miscarriage rates,[26] low birth weight, or preterm delivery.[27]

Viability and established pregnancy

A related issue that comes up in this debate is how often fertilization leads to an established, viable pregnancy. Current research suggests that fertilized embryos naturally fail to implant some 30% to 60% of the time.[28][29] Of those that do implant, about 25% are miscarried by the sixth week LMP (after the woman's Last Menstrual Period).[30] 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

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 pro-life 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 pro-life groups as immoral. This is because of the possibility of causing what they believe to be an abortion.[31]

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 pro-life groups do not consider the practice to be immoral, citing the bioethical principle of double effect.[32] 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.

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.[24] 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.[33][34]

Detectable pregnancy

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 for.

See also

External links


  1. ^ FDA Rejection of Over-The-Counter Status for Emergency Contraception Pills American Medical Association House of Delegates Resolution:443. Retrieved April 30, 2007
  2. ^ BMA (May 2005). "Abortion time limits: A briefing paper from the British Medical Association".   "The term 'abortion' is used throughout this paper to refer to the induced termination of an established pregnancy (i.e. after implantation)."
  3. ^ Hope, T. and 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.   - "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."
  4. ^ The American Heritage Stedman's Medical Dictionary, 2002
  5. ^ Larimore, Walter L., MD, et al. "Response: Does Pregnancy Begin at Fertilization?" Family Medicine, November-December 2004.
  6. ^ Doctor:George P. Pettit, M.D. (2002). "Due Date Calculator".  
    Hospital:Northwestern Memorial Hospital (2006). "What is a trimester?".  
    Medical company:The Merck Manuals Online Medical Library (2003). "Stages of Development: Pregnancy".  
  7. ^ Stein, Rob (2008-07-31). "Workers' Religious Freedom vs. Patients' Rights". Washington Post: pp. A01. Retrieved 2008-08-05.  
  8. ^ Shapiro, Joseph (2008-08-22). "HHS Backs Protections For Anti-Abortion Doctors". Washington Post. Retrieved 2008-08-24.  
  9. ^ Stein, Rob (2008-08-22). "Protections Set for Antiabortion Health Workers". Washington Post: pp. A01. Retrieved 2008-08-24.  
  10. ^ a b Webster’s Revised Unabridged Dictionary (1913 and 1828) via the ARTFL Project. See definitions of "pregnant" and "pregnancy".
  11. ^ 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, p. 284 (U. Mich. 2003).
  12. ^ Boving, B.G., "Implantation Mechanisms", in Mechanics Concerned With Conception. Hartman, C.G., ed. (Pergamon Press 1963), page 386.
  13. ^ American College of Obstetricians and Gynecologists Terminology Bulletin. Terms Used in Reference to the Fetus. No. 1. Philadelphia: Davis, September, 1965.
  14. ^ 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).
  15. ^ Hughes, E.C. "Gametogenesis and Fertilization", in Obstretric-Gynecologic Terminology. Philadelphia: Davis, 1972: 299-304.
  16. ^
  17. ^ 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. PMID 6174375.  
  18. ^ Lloyd J DuPlantis, Jr (2001). Early Pregnancy Factor. Pharmacists for Life, Intl. Retrieved 2007-01-01.  
  19. ^ "Mechanisms of the Contraceptive Action of Hormonal Methods and Intrauterine Devices (IUDs)". Family Health International. 2006. Retrieved 2006-07-05.  
  20. ^ Keller, Sarah (Winter 1996, Vol. 16, No. 2). "IUDs Block Fertilization". Network. Family Health International. Retrieved 2006-07-05.  
  21. ^ Grimes, David (2007). "Intrauterine Devices (IUDs)". in Hatcher, Robert A., et al.. Contraceptive Technology (19th rev. ed.). New York: Ardent Media. p. 120. ISBN 0-9664902-0-7.  
  22. ^ 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. PMID 6174375.  
  23. ^ Trussell, James; Elizabeth G. Raymond (April 2008) (PDF). Emergency Contraception: A Last Chance to Prevent Unintended Pregnancy. The Office of Population Research at Princeton University and the Association of Reproductive Health Professionals. Retrieved 2008-05--08.  
  24. ^ 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. PMID 1521642.  
  25. ^ Luc Bovens (2006). "The rhythm method and embryonic death". Journal of Medical Ethics 32: 355–356. doi:10.1136/jme.2005.013920. PMID 16731736.  
  26. ^ 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.  
  27. ^ 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.  
  28. ^ Kennedy, T.G. Physiology of implantation. 10th World Congress on in vitro fertilization and assisted reproduction. Vancouver, Canada, 24-28 May 1997.
  29. ^ 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.  
  30. ^ Wilcox AJ, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. New England Journal of Medicine. 1999;340(23):1796-1799. PMID 10362823.
  31. ^ Finn, J.T. (2005-04-23). ""Birth Control" Pills cause early Abortions". Pro-Life America — Facts on Abortion. Retrieved 2006-08-25.  
  32. ^ Doesn't breastfeeding do the same thing as the Pill? Eternal Perspective Ministries, 2006. Accessed May 2006.
  33. ^ "Emergency Contraception & Conscience: Christian Right Attacks on Contraceptives". Religion & Spirituality Agnosticism / Atheism. Retrieved 2006-06-22.  
  34. ^ Shorto, Russell (2006-05-07). "Contra-Contraception". New York Times Magazine. pp. 4 of 9-page online article.  

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