Science at Issue in Debate on Morning-After Pill – NYTimes.com.
Pharmer is immensely amused by the NYT Political Science article purporting that Plan B, levonorgestrel (a progestin – synthetic progesterone analog) delays ovulation but has no effect upon post fertilization mechanisms. This claim certainly has a relationship to political ideology, but not to pharmacological science.
There is the suggestion that Plan B can operate to impede ovulation even when taken 72 hours after intercourse.
The usual life of sperm is 48 hours, and The usual lifespan of secondary oocytes (eggs) is 1 day. The most fertile time for a woman is the day of, and the day after ovulation.
Laughably entertaining is the suggestion that there is no time for levonorgestrel to affect thickness or receptivity of the uterine lining, but there is time for it to always work by delaying ovulation. Scroll back up to the lifespan of the gametes and THEN ponder that it takes about 7 days for the early human embryo to travel down the fallopian tubes into the uterus and implant in the uterine lining.
Seven days is not long enough for the morning after pill to affect feedback inhibition, transport, endometrial tissue, and implantation processes, yet 48 hours is claimed to be long enough to exert a perfect 100 percent mechanism for delaying ovulation so that sperm and ‘egg’ don’t meet. (Remember when a woman is most fertile, the day of and the day after ovulation?) It’s pathetic when leftist ideology replaces scientific analysis and inquiry in such a blatantly obvious manner.
James Trussell (population controller of Princeton) has changed his tune about the efficacy of Plan B. Now he wants to say that the pill is ridiculously ineffective, so that condoms, rhythm, and withdrawal are far superior in efficacy as birth control. This is what he needs to admit in order to claim that the Plan B doesn’t work if a woman has ovulated.
Progesterone hormones have multiple mechanisms of action. Progesterone receptors are found in various tissues, and their preponderance and activity undergo cyclic changes. These hormones largely affect gene expression. These effects are not instantaneous. The physiological effects of progestins on reproduction vary with the timing of their use. The morning after pill’s modes of action will vary depending on when in the cycle and how long after intercourse they are used.
One cannot prescribe progestins to patients to mitigate hypermenorrhea (excessive bleeding), and at the same time claim that they don’t affect the uterine lining.
Progestins given on a scheduled basis fail to prevent ovulation in about half of patients. This has been attached to the labeling of progestin only pills, which have been used to control excessive bleeding, as well as to prevent pregnancy.
Plan B is a progestin. Ella is a selective progesterone receptor blocker (like mifepristone, RU456). Each one will affect the reproductive processes in different, dose dependent and time dependent ways. Political Science author Pam Belluck needs to consider the drugs separately when attempting to evaluate them mechanistically.
Plan B, levonorgestrel, like ALL hormones, operates on many physiological processes, by many different means.
If the leftists ever manage to develop effective birth control drugs which operate ONLY by preventing the union of sperm and egg, we may proceed with the constitutional amendments to accurately define human life with no further impediments.
More at Jill Stanek’s place. and right HERE.