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Beginning of pregnancy controversy



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 might be abortifacient. The controversy is not a scientific issue since knowledge of human reproduction and development has become very refined and scientists generally avoid describing facts using terminology with emotional or political overtones. Rather, the issue has social, political and legal ramifications since, rightly or wrongly, some equate the 'beginning of pregnancy' with the 'beginning of life'. The latter question also has no scientific definition since, from a biological standpoint, life is a continuum without a discrete starting point.

Additional recommended knowledge

Contents

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.

The American Medical Association has stated 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.

Beginning of the controversy

Previously, pregnancy was defined in terms of conception. However, in the absence of an accurate understanding of human development, early notions about the timing and process of conception were often vague. For example, Webster's Dictionary defines "pregnant" (or "pregnancy") as "having conceived" (or "the state of a female who has conceived"), in its 1828 and 1913 editions.[7]

Both the 1828 and 1913 editions of Webster's Dictionary said that to "conceive" meant "to begin the formation of the embryo." 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.[8]

In 1959, Dr. Bent Boving suggested that the word "conception" should be associated with the process of implantation instead of fertilization.[9] 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."[10]

The 1965 ACOG definition was imprecise because, by the time it implants, the zygote is called a blastocyst,[11] so it was clarified in 1972 to "Conception is the implantation of the blastocyst."[12] Some dictionaries continue to use the definition of conception as the formation of a viable zygote.[13]

Birth control - mechanism of action

See also 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 back-up effect of preventing implantation, thus allowing the zygote to die. Those who define pregnancy from fertilization subsequently 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.[14] and a study of the combined oral contraceptive pill has been proposed.[15]

Possibly affected methods

  • Hormonal contraception works primarily by preventing ovulation, but may have a secondary effect of interfering with implantation of embryos.
  • Intrauterine devices work primarily by spermicidal/ovicidal effects, but may have a secondary effect of interfering with the development of pre-implanted embryos.
  • 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.[16]
  • Fertility awareness methods work primarily by preventing conception, but it has been speculated they have a secondary effect of creating embryos incapable of implanting (due to aged gametes at the time of fertilization).[17]

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, including emergency contraception, 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.[18]

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.[19] 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.[16] 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.[20][21]

In vitro fertilisation and detectable pregnancy

The advent of in vitro fertilisation allowed fertilisation to occur in a Petri dish instead of inside a woman. This clearly made fertilization an event that did not automatically result in 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.

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.[22][23] Of those that do implant, about 25% are miscarried by the sixth week LMP (after the woman's Last Menstrual Period).[24] As a result, even without the use of birth control, between 48% and 70% of zygotes never result in established pregnancies, much less birth.

Notes

  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 Appendix 3: Some key points in the law on abortion and fetal damage. The Oxford Centre for Ethics and Communication in Health Care Practice, Oxford University. - "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. ^ Webster’s Revised Unabridged Dictionary.
  8. ^ 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).
  9. ^ Boving, B.G., "Implantation Mechanisms", in Mechanics Concerned With Conception. Hartman, C.G., ed. (Pergamon Press 1963), page 386.
  10. ^ American College of Obstetricians and Gynecologists Terminology Bulletin. Terms Used in Reference to the Fetus. No. 1. Philadelphia: Davis, September, 1965.
  11. ^ 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).
  12. ^ Hughes, E.C. "Gametogenesis and Fertilization", in Obstretric-Gynecologic Terminology. Philadelphia: Davis, 1972: 299-304.
  13. ^ Dictionary.com.
  14. ^ 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. 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.
  15. ^ Lloyd J DuPlantis, Jr (2001). "Early Pregnancy Factor". Pharmacists for Life, Intl. Retrieved on 2007-01-01.
  16. ^ 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.
  17. ^ Luc Bovens (2006). "The rhythm method and embryonic death". Journal of Medical Ethics 32: 355-356.
  18. ^ Finn, J.T. (2005-04-23). "Birth Control" Pills cause early Abortions. Pro-Life America — Facts on Abortion. prolife.com. Retrieved on 2006-08-25.
  19. ^ Doesn't breastfeeding do the same thing as the Pill? Eternal Perspective Ministries, 2006. Accessed May 2006.
  20. ^ Emergency Contraception & Conscience: Christian Right Attacks on Contraceptives. About.com Religion & Spirituality Agnosticism / Atheism. Retrieved on 2006-06-22.
  21. ^ Shorto, Russell. "Contra-Contraception", New York Times Magazine, May 7, 2006, pp. 4 of 9-page online article. 
  22. ^ Kennedy, T.G. Physiology of implantation. 10th World Congress on in vitro fertilization and assisted reproduction. Vancouver, Canada, 24-28 May 1997.
  23. ^ 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.
  24. ^ 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.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Beginning_of_pregnancy_controversy". A list of authors is available in Wikipedia.
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