Volume 75, Issue 2, Pages 112-118 (February 2007)
Effectiveness of levonorgestrel emergency contraception given before or after ovulation
Natalia Novikovaa, Edith Weisbergab, Frank Z. Stanczykc, Horacio B. Croxattod, Ian S. Fraserab
How Plan B Works
It does not cause the uterus to be a hostile environment. It actually does the opposite. Plan B is the hormone progesterone , which is the same hormone fertility clinics give women to maintain the uterine lining for keeping a pregnancy.
Progesterone helps maintain the uterine lining, but also suppresses LH production by the pituitary.
This is why women undergoing fertility treatment are sometimes given progesterone to help maintain the pregnancy.
No evidence Plan B causes implantation failure
There is evidence that suggests that Plan B only prevents conception by either making cervical mucus hostile to sperm or preventing ovulation.
Where the lie about Plan B and Birth Control Pills as causing abortion started:
'The post-fertilization effect was purely a speculation that became truth by repetition,' says Joe DeCook, MD, a retired OB/GYN and vice president of the American Association of Pro-Life Obstetricians and Gynecologists.
started, and that was from looking at women on the pill. If there is no ovulation, there is no cascade of events leading to thickening of the uterine lining so implantation can take place. That's the "hostile environment". However, you can only have an insufficient uterine lining of there is no ovulation. The notion of ovulation occurring while a woman was on the pill, getting fertilized, and not implanting was based on the notion that women on the pill have an insuficient uterine lining. What was not taken onto consideration was the fact that if ovulation occurred while on the pill, the cascade of events leading to a thickening, sufficient for pregnancy uterine lining would also occur.
Otherwise, you'd never hear of a woman giving birth after getting pregnant while on the pill. If Plan B stopped fertilized eggs from implanting, it would work a lot longer than 5 days after sex, and it would work a lot better.
In order to classify Plan B and Birth Control Pills as abortifacients, several things must exist:
1. Conceptions must occur.
2. The abortive effect must be present with proper use as prescribed.
3. Loss of these conceptions must exceed the base-line loss for populations not using this substance, or be shown to occur due solely to the medication itself, and not other known factors.
4. The abortive effect should be consistent and reproducible by multiple independent observers.
Studies show Plan B does not interfere with implantation
(H.B. Croxatto et al. Contraception 70 (2004) 442–450)
Durand, et.al. (M. Durand et al. Contraception 71 (2005) 451– 457)
The Christian Medical Association with its more than 18,000 membership disagree with Randy Alcorn’s position, as do I in my book Contraception Guidebook.
There is currently no convincing medical evidence to support the theory of “uterine lining hostility” and much evidence to refute it.
Recent research by members of the
Population Council’s International Committee
for Contraception Research (ICCR) and other
scientists shows that the most popular method
of emergency contraception appears to work by
interfering with ovulation,thus preventing fer-
tilization,and not by disrupting events that
occur after fertilization.
Croxatto, H.B., V. Brache, M. Pavez, L. Cochon, M.L.
Forcelledo, F. Alvarez, R. Massai, A. Faundes, and
A.M. Salvatierra. 2004. “Pituitary–ovarian function fol-
lowing the standard levonorgestrel emergency con-
traceptive dose or a single 0.75-mg dose given on
the days preceding ovulation,” Contraception70(6):
Ortiz, M.E., R.E. Ortiz, M.A. Fuentes, V. H. Parraguez,
and H.B. Croxatto. 2004. “Post-coital administration
of levonorgestrel does not interfere with post-fertil-
ization events in the new-world monkey Cebus
apella,” Human Reproduction19: 1352–1356.
Muller, A.L., C.M. Llados, and H.B. Croxatto. 2003.
“Postcoital treatment with levonorgestrel does not
disrupt postfertilization events in the rat,”
Emergency Contraception’s Mode of Action Clarified
[R]ecent solid investigations they have demonstrated that evidences do not exist, direct nor indirect, of effects post-fertilization on the endometrium that interfere with the implantation. One has not either demonstrated that the methods of Contraception of Emergency contemplated
Croxatto HB, Ortiz ME, Müller AL. Mechanisms of action of emergency contraception. Steroids 2003;68:1095-98.
Catholic Church Ok’s Plan B
Outrage on Plan B, So Why Not the Pill?
"The pervasive myth out there is that emergency contraception is an abortifacient," said Dr. David Archer, director of clinical research at the Contraceptive Research and Development Program of Eastern Virginia Medical School in Norfolk. "But there's no evidence scientifically that that's true."
For one thing, Archer points out, emergency contraception generally doesn't work if taken after a woman has ovulated.
Published evidence clearly indicates that Plan B can interfere with sperm migration by altering the cervical and uterine environment, and that preovulatory use of Plan B usually suppresses the LH surge either completely or partially, which in turn either prevents ovulation or leads to the release of ova that are resistant to fertilization. Epidemiological evidence rules strongly against interruption of fallopian tube function by Plan B. Evidence that would support direct involvement of endometrial damage or luteal dysfunction in Plan B's contraceptive mechanism is either weak or lacking altogether. Both epidemiologic and clinical studies of Plan B's efficacy in relation to the timing of ovulation are inconsistent with the hypothesis that Plan B acts to prevent implantation.
Progestational drugs, including levonorgestrel, are used therapeutically in assisted reproduction because they increase the rate of successful implantation and pregnancy.
According to the literature that they distribute, plan B is an abortifacient - it causes abortions. So therefore, they line up against it. (It is also often confused with RU-486, which is an abortifacient)
But there is no evidence for this claim. The progesterone in the pill suppresses follicle development, preventing the release of an egg. It has not been found to prevent implantation, and in fact, progesterone is used in fertility treatments to encourage implantation! Their claim allegedly stems from the fact that the uterine lining thins a little when plan B is taken. However, the medical community rejects the notion that plan B acts in this way at all.
There is ABSOLUTELY NO CLINICAL EVIDENCE FOR ANY EFFECT OTHER THAN ON OVULATION.
Why would levonorgestrel, a progesterone agonist that mimics the effect of progesterone, prevent implantation, when progesterone produced from the corpus luteum immediately after ovulation actually promotes implantation by converting the endometrium to decidua? Answer: It does not.
Plan B Causes Less Embryo Loss than not Using it
Nevertheless, even if in some cases ECPs work by inhibiting subsequent implantation of a fertilized egg, these probably would be outnumbered by other cases in which fertilization of an egg that would not have subsequently implanted naturally is prevented because ECPs inhibited ovulation. Therefore, on balance, ECPs probably reduce the incidence of fertilized eggs that do not subsequently implant.
"PROF. SANDEL: [W]hat percent of fertilized eggs fail to implant or are otherwise lost?
DR. OPITZ: The answer to your first question is that it is enormous. Estimates range all the way from 60 percent to 80 percent of the very earliest stages, cleavage stages, for example, that are lost."
If so many die in the natural course of things, how do we not treat natural procreation as a great fountain of tragedy and carnage?
"We now know that for every successful pregnancy which results in a live birth, many, perhaps as many as five, early embryos will be lost or 'miscarry' (although these are not perhaps miscarriages' as the term is normally used, because this sort of very early embryo loss is almost always entirely unnoticed).
How are we to think of the decision to have a child in the light of these facts? One obvious and inescapable conclusion is that God and/or nature has ordained that 'spare' embryos be produced for almost every pregnancy, and that most of these will have to die in order that a sibling embryo can come to birth. Thus the sacrifice of embryos seems to be an inescapable and inevitable part of the process of procreation. .**"
Hormonal birth control does not cause embryos not to implant:
Ovulation causes theuterine lining to thicken. Women on the pill do not ovulate, so their uterine linings are thinner, which is why some anti-birth control people say the fertilized eggs won't be able to implant, because the lining isn't thick enough. What they didn't mention in that in order for a woman to have a fertilized egg in the first place, while she is on the pill, ovulation must take place. Ovulation thickens the lining. In other words, if a woman ovulates while on the pill, her uterine lining will thicken and the fertilized egg will implant.
As to how that lie that Plan B and birth control pills cause abortions got started:
"Consensus comes from a surprising source. "The post-fertilization effect was purely a speculation that became truth by repetition," says Joe DeCook, MD, a retired OB/GYN and vice president of the American Association of Pro-Life Obstetricians and Gynecologists. "In our group the feelings are split. We say
it should be each doctor's own decision, because there is no proof."
Another interesting thing about this misconception is that there is something that actually does cause fertilized eggs to die, and that is breastfeeding.
Breastfeeding is an Abortifacient
"Trussell said he supports doctors who say women need to know it's possible that emergency contraception may affect embryo implantation. But that's true for nearly all methods of contraception, he added - including breast-feeding.
Breast-feeding, which can have a contraceptive effect up to six months after the birth of a child, also causes changes in the uterine lining. In that respect, it carries the same possibility of interfering with implantation."
"Breastfeeding causes more embryo loss than hormonal birth control."
Breast-Feeding Kills The pro-life case against birth control, nursing, and exercise.