The terms 'pre-implantation contraception' (PIC) and 'emergency contraception' (EC) as well as, 'post-coital contraception' (PCC) are synonymous expressions inaccurately used to describe the administration of a drug or use of a device post intercourse, with the explicit intention of stopping implantation of a newly created human embryo. These three terms are also collectively referred to, in both the lay and medical literature, as the 'morning-after' pill. (MAP)

Procedures included in the post-coital method of birth control are the administration of high (supra-physiological) oral doses of either synthetic female hormones in combination (ethinyl estradiol and levonorgestrel), or the solitary use of synthetic progesterone (levonorgestrel). The copper-bearing intra-uterine device (IUD) is also promoted as emergency 'contraception'(1) as is the use of mifepristone (RU-486). (2) Via a multitude of attack points, these drugs or devices can obstruct the complex and highly sophisticated process of implantation of the human embryo in the maternal endometrium (womb). (3) The expression 'attack points' describes the many interdependent events during the delicate process of implantation and attachment of the embryo which are vulnerable to interference.

Associated with these medical procedures are many definitions and concepts that are intermingled, interchanged or redefined either out of genuine ignorance, or for ideological, political, or tactical reasons. Immediately one can cite the almost universally misuse of the term contraception. This semantic error is not an isolated occurrence. Were it so, correction of this solitary term would be both brief in length and wide-ranging in impact.

Rather, the term contraception is extensively underpinned by a foundation of erroneously defined terms from both embryology and pharmacology. In scientific and lay publications, the terms conception, pregnancy, pregnant, abortion and abortifacient are misused by authors and consequently misunderstood by readers. Furthermore, definitional errors become the bedrock of poorly informed and poorly framed social laws.

With these problems in mind, this lexicon entry will set out the definitions of the aforementioned terms, and will also incorporate examples of how these terms have been altered so they are no longer connected with their authentic scientific origins and meaning. This will be followed by an overview of the modus operandi of pre-implantation/emergency/post-coital 'contraception'. Discussion will also cover the use of RU-486 (mifepristone) as pre-implantation/emergency 'contraception' and briefly, the copper-bearing intra-uterine device (IUD). Linked to each topic will be a review of how the respective methods act as a post-coital abortifacient. Complementing this discussion will be a summary of newer research findings on the complexity of the process of attachment and implantation of the human embryo, and the adverse impact supra-physiological levels of artificial hormones can have on this process.

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(1) Rosenfield A. Emergency contraception: a modality whose time has come. J Amer Med Women's Assoc

(2) Cameron ST, Critchley H, Buckley CH, Kelly RW, Baird DT. Effect of two antiprogestins (mifepristone and onapristone) on endometrial factors of potential importance for implantation. Fert Steril 1997; 67 (6): 1046-1053

(3) Bowen JA, Hunt JS. The role of integrins in reproduction. P.S.E.B.M. 2000; 233:331-343