Contraception - Chemical Methods / Hormonal Contraception / Emergency / Morning After Pill

Mechanism of Emergency Contraception

Emergency Contraceptive Pills. [Again,] one must be careful of the terminology. Many now speak of "conception" as that moment when the human blastocyst, the early ball of approximately 100 cells, actually implants in the mother’s uterus (womb).

The time from actual fertilization (sperm and egg unite in the Fallopian Tube) until implantation, a period of about 7-10 days, is ignored by this definition, even though no genetic change occurs in the cells during this time period.

Many family planning specialists who have supported the terminology change can thus rationalize that the destruction of the human embryo between fertilization and implantation should be labeled "contraception", rather than "early abortion".

[American Association of Pro-Life Obstetricians & Gynecologists]


What are hormonal ECPs?

The regimen approved by the FDA for post-coital "contraception" identifies 6 brands of ordinary birth control pills (OCs), containing estrogen and progestin, and requires that a high dose of such pills be taken within 72 hours of "unprotected intercourse", followed by a second high dose 12 hours later.

How do hormonal ECPs work?

According to the FDA, "EC pills…act by delaying or inhibiting ovulation, and/or altering tubal transport of sperm and/or ova (thereby inhibiting fertilization), and/or altering the endometrium (thereby inhibiting implantation)." [emphasis added] [FDA, Federal Register Notice, Vol. 62, No. 37, 25Feb97]

These properties of OCs have long been acknowledged, but it is impossible to determine which mode of action is responsible in any given cycle for a woman’s failure to conceive or maintain pregnancy after "unprotected" intercourse.

Different modes of action occur depending upon where a woman is in her monthly cycle when intercourse occurs and when the doses of ECPs are given.

Beginning four days before ovulation, the average likelihood of conception from intercourse jumps from 0% to 11%. It rises to 30% on the day preceding, and day of, ovulation, before dropping to 9%, 5% and 0% on the three subsequent days.

If the woman is in a non-fertile time, that is, an egg or imminent egg is not available to be fertilized, then the ECPs would have no effect. Once the woman is in her fertile phase, "taking a high level of estrogen via ECPs within 72 hours of intercourse…may, in fact, precipitate ovulation. This would make it more likely, rather than less, that fertilization will occur", according to Hannah Klaus, M.D., FACOG.

This may also increase the risk of ectopic (tubal) pregnancy [Morris, J, and Van Wagenen, G., "Interception: the Use of Postovulatory Estrogens to Prevent Implantation,", Am Journal Obstet Gynecol, 115: 101-6 (1973); Diana Rabone, M.D., "Postcoital Contraception – Coping With the Morning After", "Current Therapeutics", 1990, cited in Wilks, "A Consumer’s Guide to the Pill and Other Drugs", 2nd ed, 1997, p. 156].

If an egg (ovum) is in the Fallopiam tube, the process of fertilization may begin within 15 to 30 minutes after intercourse.

The "Morning After" is already too late for any true "contraceptive" effect to intervene.

Thus some researchers conclude that "post-coital drugs act principally to terminate a viable pregnancy by interfering with the endometrium:…’ this mode of action could explain the majority of cases where pregnancies are prevented by the morning-after pill’" [Wilks, op.cit. p.154, citing Grou, F. and I. Rodriges, "The morning-after pill: How long after?", Am Journal Obstet Gynecol, 171: 1529-34 (1994)] [Life Insight, 9/1998; Family Resources Center News, 1/99]

 The morning-after pill, which contains high doses of a hormone used in birth control pills, was approved by the FDA as a prescription drug in 1998. According to this 12/03 news item, "if taken within 72 hours of unprotected intercourse, it prevents 89% of pregnancies". 

[12/29/2003  USA Today; 30 Dec 2003 Pro-Life E-News]

The article does not explain the word "prevents".  For those who promote the use of these substances, in present day terminology, "pregnancy" does not begin until implantation, about 7-10 days after fertilization.

We can not know from this description if fertilization is actually prevented 89% of the time, if fertilized zygotes, developing as multicellular human embryos, are aborted 89% of the time, or a combination of both occurs. Regardless, no mention is given to what becomes of the other 11% …