Contragestion

An intrauterine device.

Contragestion is the prevention of implantation of the blastocyst, or a device or substance which can effect such prevention as a means of birth control. Other birth control methods include contraception, which prevents fertilization, and abortion, the removal or expulsion of a fetus or embryo from the uterus). Contragestives include intrauterine devices placed inside the uterus and some forms of hormonal "emergency contraception".^[1]

Terminology

The term, 'contraception' is a contraction of 'contra', which means 'against', and the word 'conception', which is a non-technical term that is synonymous^[2] with fertilization. The word 'contragestion' is likewise a combination of 'contra' and 'gestation'. French scientist Étienne-Émile Baulieu coined the word in 1985 because he felt that there was a need for a technical term to describe the prevention of implantation, which did not fit the traditional definitions of either 'contraception' or 'abortion'^[3]. Elisabeth Johannisson of the International Committee for Research in Reproduction endorsed the use of this nomenclature saying that, "it is appropriately descriptive and fits in with contemporary medical ethics, which require us to indicate (when we know them) the phenomena which occur in patients. The word 'contraception' is ambiguous and 'abortion' remains the traumatic symbol of a painful failure... Faced with the imprecision of these currently used terms, 'contragestion' is preferable because it takes recent scientific knowledge into account. At the same time, it is difficult to make this term accepted because more classical expressions have great force. The word 'abortion' has a long tradition... The word 'contraception' has had a strong impact on the history of our century. Between the two it is difficult to find a place, either biological or semantic."^[4] It is also worth noting that since 18 U.S. states define pregnancy as beginning at conception,^[5] describing methods of birth control in terms of their potential means of action allows one to be technically accurate while using language that is neutral with regard to the abortifacient versus contraceptive controversy.

Contragestion and birth control

The function of birth control can be classified by the stage of reproduction during which it is active. A form of birth control which prevents the sperm from fertilizing the egg is a contraceptive agent^[6]. A form of birth control which acts after fertilization to prevent or interrupt the implantation of the embryo into the uterine lining is a contragestive agent.^[7] After implantation has occurred, an agent which ends gestation by terminating the pregnancy is an abortifacient^[8]

• Contraception occurs when an agent prevent the sperm from fertilizing the egg^[9]
• Contragestion occurs when an agent prevents or interrupts implantation of the embryo or causes the uterine lining to shed during the implantation period^[10]
• An abortion has taken place if, after implantation has occurred, an abortifacient terminates the pregnancy before the fetus achieves viability.^[11]

It is important to bear in mind that these mechanisms of action are not mutually exclusive. One substance or device can have more than one potential effect depending upon when it is used. For example, while mifepristone is best known as an abortifacient, it can also function as a contragestive agent.^[12] Likewise, the IUD can be used as a contraceptive or a contragestive depending upon when it is inserted.^[13]

Naturally occurring contragestion

Implantation is a delicate and complicated process which can be affected by a variety of factors. The result is that contragestion occurs naturally in both humans and other animals for many reasons.

In animals

One factor which can cause contragestion is malnutrition. For example, a deficiency of vitamin A can cause contragestion in cats ^[14] and studies indicate that insufficient calcitonin causes contragestion in rats. ^[15] Rodents also display something called the Bruce effect wherein exposure to the scent of an unfamiliar male causes contragestion. ^[16] Environmental factors are also a cause of contragestion. Toxins can cause contragestion in both animals and humans, with exposure to dioxins preventing 70% of implantation of mouse embryos. ^[17]

In humans

Contragestion is a relatively common occurrence in humans. Estimates of the rate of contragestion within the human population as a whole vary greatly, from as low as 30% to as high as 70%,^[18] with actual testing of healthy women attempting conception revealing a rate of 36%.^[19] Many embryos are incapable of implantation because they are not properly formed. According to Lynn Wiley, professor of obstetrics and gynecology, "Only certain cells within the embryo can implant and form a placenta. Without these cells, or if these cells are not healthy, implantation will fail."^[20] Features of the uterine environment can also cause contragestion. These features include, but are not limited to anatomic abnormalities, hormonal irregularities, and malfunctions in the immune system.^[21]

See also

• Birth Control
• Beginning of pregnancy controversy
• Reproductive technology

References

1. ^ [1] Ammer, Christine; Manson, JoAnn E, & Brigham, Elizabeth F. (2009). The Encyclopaedia of Women’s Health. Infobase Publishing. pp. 2. ISBN 9780816074075.
2. ^ [2] The American Heritage Medical Dictionary Copyright 2007, 2004, page 120.
   [3] Melloni's Pocket Medical Dictionary By June L. Melloni, Ida G. Dox, B. John Melloni, Gilbert M. Eisner, Published by Informa Health Care, 2003, page 84.
   [4] Dorland's Illustrated Medical Dictionary. Philadelphia, PA: Elsevier Health Sciences. (2007). Retrieved May 26, 2009.
   [5] Churchill Livingstone's Dictionary of Nursing. Philadelphia, PA: Elsevier Health Sciences. (2006) Retrieved May 26, 2009.
   [6] Black's Medical Dictionary, 41st Edition. London: A&C Black. (2006).Retrieved May 27, 2009
3. ^ [7] Contragestion and other Clinical Applications of RU 486, an Antiprogesterone at the Receptor, Etienne-Emile Baulieu Science, New Series, Vol. 245, No. 4924 (Sep. 22, 1989), pp. 1351-1357 Published by: American Association for the Advancement of Science Retrieved May 26, 2009.
4. ^ [8] Assessment of research and service needs in reproductive health in Eastern Europe, Elisabeth Johannisson. Published by Taylor & Francis, (1997), pp. 53-54.
5. ^ [9] The Social Life of Emergency Contraception in the United States: Disciplining Pharmaceutical Use, Disciplining Sexuality, and Constructing Zygotic Bodies by L. L. Wynn, James Trussell Medical Anthropology Quarterly, Volume 20. Issue 3. September 2006 (Page 317)Retrieved May 26, 2009.
6. ^ [10] Melloni's Pocket Medical Dictionary By June L. Melloni, Ida G. Dox, B. John Melloni, Gilbert M. Eisner, Published by Informa Health Care, 2003, page 86.
   [11] Encyclopedia of Business Ethics and Society By Robert W. Kolb; Published by SAGE, copyright 2007. page 176.
   [12] Dorland's Illustrated Medical Dictionary. Philadelphia, PA: Elsevier Health Sciences. (2007). Retrieved May 26, 2009.
   [13] Churchill Livingstone's Dictionary of Nursing. Philadelphia, PA: Elsevier Health Sciences. (2006) Retrieved May 26, 2009.
7. ^ [14] The American Heritage Medical Dictionary, Houghton Mifflin Harcourt; Copyright May 2008. page 124.
   [15] Lifting the Scientifc Veil: Science Appreciation for the Nonscientist By Paul Sukys; Published by Rowman & Littlefield, 1999. Glossary (page 511).
   [16] Legal Aspects of Child Health Care By Judith Hendrick; Nelson Thornes Publishing, Ltd., 1997 page 103.
   [17] Encyclopedia of Business Ethics and Society By Robert W. Kolb; Published by SAGE, copyright 2007. page 176.
8. ^ [18] Melloni's Pocket Medical Dictionary By June L. Melloni, Ida G. Dox, B. John Melloni, Gilbert M. Eisner, Published by Informa Health Care, 2003, page 1.
   [19] The American Heritage Medical Dictionary. Boston, MA: Houghton Mifflin. (2007)Retrieved May 26, 2009
   [20] Churchill Livingstone's Dictionary of Nursing. Philadelphia, PA: Elsevier Health Sciences. (2006) Retrieved May 26, 2009.
   [21] Dorland's Illustrated Medical Dictionary. Philadelphia, PA: Elsevier Health Sciences. (2007). Retrieved May 26, 2009.
   [22] Collins Dictionary of Medicine. London: Collins.(2005) Retrieved May 26, 2009
9. ^ [23] Melloni's Pocket Medical Dictionary By June L. Melloni, Ida G. Dox, B. John Melloni, Gilbert M. Eisner, Published by Informa Health Care, 2003, page 86.
   [24] Legal Aspects of Child Health Care By Judith Hendrick; Nelson Thornes Publishing, Ltd., 1997 page 103.
   [25] Human Life Before Birth: Introductory Embryology By Frank Dye; Published by CRC Press, glossary page 234.
   [26] Black's Medical Dictionary By Cyril William Holmes Havard Published by Rowman & Littlefield, 1990. page 164.
10. ^ [27] The Chambers Dictionary, Allied Publishers; Copyright 1998. page 355.
    [28] Human Life Before Birth: Introductory Embryology By Frank Dye; Published by CRC Press, glossary page 234.
11. ^ [29]Churchill Livingstone's Dictionary of Nursing. Philadelphia, PA: Elsevier Health Sciences. Retrieved May 26, 2009 (2006) Retrieved May 26, 2009.
    [30] The American Heritage Medical Dictionary. Boston, MA: Houghton Mifflin. Retrieved May 26, 2009 (2007) Retrieved May 26, 2009.
    [31] Dorland's Illustrated Medical Dictionary. Philadelphia, PA: Elsevier Health Sciences. Retrieved May 26, 2009 (2007) Retrieved May 26, 2009.
12. ^ [32] Contragestion and other Clinical Applications of RU 486, an Antiprogesterone at the Receptor, Etienne-Emile Baulieu Science, New Series, Vol. 245, No. 4924 (Sep. 22, 1989), pp. 1351-1357 Published by: American Association for the Advancement of Science Retrieved May 26, 2009.
13. ^ [33] Emergency: Emergency Contraception Bobbi J. Morris, Cathy Young, Kathleen Kearney, The American Journal of Nursing, Vol. 100, No. 9 (Sep., 2000), pp. 47 Published by: Lippincott Williams & Wilkins Retrieved May 26, 2009.
14. ^ [34]Nutrition in Cats By: PetPlace Veterinarians
15. ^ [35]Embryo implantation: molecular, cellular, and clinical aspects By Daniel D. Carson page 89
16. ^ [36]Infanticide by males and its implications By Carel van Schaik, Charles Helmar Janson Page 353
17. ^ [37] UC Davis Magazine- The Facts of Life by Karen Guin
18. ^ Physiology of implantationKennedy, T.G. Physiology of implantation. 10th World Congress on in vitro fertilization and assisted reproduction. Vancouver, Canada, 24–28 May 1997
19. ^ [38]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
20. ^ [39]UC Davis Magazine- The Facts of Life by Karen Guin
21. ^ [40]Reproductive Medicine Institute- Treating the Problem Prior to Implantation