Over at HMS blog is an interesting thread on rape and pregnancy prevention. The discussion centers around the use of high doses of female hormones to disrupt the menstrual cycle and prevent ovulation (and hence fertilization). This is one of the mechanisms of action of the so-called morning-after pill (aka emergnecy contraception or ECP). However, there are several mechanisms by which these medications act. One is that they disrupt the menstrual cycle. Dependant upon where in the cycle the hormones are given, they can prevent ovulation, delay ovulation, or have no effect on ovulation. They can disrupt the formation of the uterine lining so that implantation cannot occur (very early chemical abortion). They also cause thickening of the cervical mucous and can make sperm penetration difficult or impossible (however, that is not protective after rape, as the mucous is either present or not present at the time of insemination, and fertile mucous transports sperm pretty rapidly to a waiting egg, whereas infertile or no mucous is pretty much a death trap for the sperm).
I am not near my NFP texts right now and don't remember exactly what the transport and survival time is for healthy sperm in fertile mucous - Is there enough time that disruption of ovulation would be the actual mechanism of action for pregnancy prevention?
I don't think we really have enough knowledge on some of this to endorse any specific post-facto method of preventing pregnancy in rape victims (that is not abortifacient).
One thing that few people realize is that there are really very few days of fertility in every cycle, the recent University of Saskatchewan study notwithstanding. The problem for NFP is iidentifying those days with enough precision to make behavioural recommendations. The likelihood of conception related to a single incident is variable dependant upon the time within the menstrual cycle, which is data that can be teased out of the ECP studies - the reason these pills seem to be so effective is that most of the time the women weren't in their fertile days anyhow!

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This page contains a single entry by alicia published on July 15, 2003 5:24 PM.

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