Beginning of pregnancy controversy

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Controversy over the beginning of pregnancy usually occurs in the context of the abortion debate. Different definitions are used to define certain birth control methods as either contraceptives or abortifacients, because of their possible post-fertilisation effects.

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[edit] Definitions of pregnancy beginning

Traditionally, doctors have measured pregnancy from a number of convenient points, including the day of last menstruation, ovulation, fertilisation, 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 definition of pregnancy as starting from implantation has been adopted by the American Medical Association. Likewise, the British Medical Association defines pregnancy from implantation,[1][2] and this is the legal definition in the United Kingdom.[3]

Despite this, other definitions are frequently used. The American Heritage® Stedman's Medical Dictionary defines "pregnancy" as "from conception until birth." [4] Prominent medical textbooks such as Langman's Medical Embryology count pregnancy from fertilisation,[5] Professionals have also debated the issue in medical journals.[6]

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.[7] However in this system, ovulation and fertilisation do not occur until 2 out of the 40 weeks counted have passed.

[edit] Types of contraception

Birth control methods usually prevent either fertilisation or implantation. Those that prevent fertilisation cannot be seen as abortifacient because, by any of the above definitions, pregnancy has not started. However, some agents have a proposed back-up effect of preventing implantation and thus destroying the blastocyst, and are therefore labeled as abortifacient by those that classify the start of pregnancy as fertilisation.

[edit] Possibly affected birth control 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.[8]
  • 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 fertilisation).[9]

[edit] Ethics of preventing pregnancy

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.[10]

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.[11] 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 fertilisation.[8] 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.[12][13]

[edit] 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 fertilisation an event that did not automatically result in pregnancy.

All 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 tested for.

[edit] Viability and established pregnancy

A related issue that comes up in this debate is how often fertilisation leads to an established, viable pregnancy. Current research suggests that fertilised embryos naturally fail to implant some 30% to 60% of the time.[14] Of those that do implant, about 25% are miscarried in the first two weeks after pregnancy can be detected.[15] As a result, the majority of zygotes never result in established pregnancies, much less birth.

[edit] Notes

  1. ^ British Medical Association (December 1999). The law and ethics of abortion: Conscientious objection clause.
  2. ^ BMA (May 2005). Abortion time limits: A briefing paper from the British Medical Association.
  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. - See the section 'Inter-uterine contraceptive devices (IUCDs) and "morning after" pills'
  4. ^ The American Heritage® Stedman's Medical Dictionary, 2002
  5. ^ O'Brian, Patrick and Thomas Sadler. Langman's Medical Embryology. Lippincott Williams & Wilkins (2004), p. 117.
  6. ^ Larimore, Walter L., MD, et al. "Response: Does Pregnancy Begin at Fertilization?" Family Medicine, November-December 2004.
  7. ^ 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.
  8. ^ 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.
  9. ^ Luc Bovens (2006). "The rhythm method and embryonic death". Journal of Medical Ethics 32: 355-356.
  10. ^ 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.
  11. ^ Doesn't breastfeeding do the same thing as the Pill? Eternal Perspective Ministries, 2006. Accessed May 2006.
  12. ^ Emergency Contraception & Conscience: Christian Right Attacks on Contraceptives. About.com Religion & Spirituality Agnosticism / Atheism. Retrieved on 2006-06-22.
  13. ^ Shorto, Russell. "Contra-Contraception", New York Times Magazine, May 7, 2006, pp. 4 of 9-page online article.
  14. ^ Kennedy, T.G. Physiology of implantation. 10th World Congress on in vitro fertilisation and assisted reproduction. Vancouver, Canada, 24-28 May 1997.
  15. ^ 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.
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