A New York Times analysis has found that the morning-after pill — drugs including Plan B One-Step and Ella, which are taken to prevent pregnancy after sex — do so not by keeping fertilized eggs from implanting in the womb, but by delaying ovulation. Some pills also thicken cervical mucus so that sperm have difficulty swimming. However, labels on the inside of boxes for the pills say they may work by blocking fertilized eggs from implanting in a woman’s uterus — descriptions that have led to some religious groups, conservative politicians and others to claim that the pills cause abortion.
Dr. Donna Harrison, director of research for the American Association of Pro-life Obstetricians and Gynecologists, says that using the pills is the “moral equivalent of homicide.”
Mitt Romney has been more straightforward, dubbing morning-after pills as “abortive pills.”
While the websites of medical authorities, including the National Institutes of Health and the Mayo Clinic, have said that emergency contraceptives may prevent implantation of a fertilized egg, the New York Times has discovered that such a result is not borne out in scientific studies and that
It turns out that the politically charged debate over morning-after pills and abortion, a divisive issue in this election year, is probably rooted in outdated or incorrect scientific guesses about how the pills work.” [my emphasis]
These findings about how emergency contraceptives work would mean that drugs like Plan B One-Step and Ella “would not meet abortion opponents’ definition of abortion-inducing drugs.” In contrast, RU-486 can be called an abortion pill “because it destroys implanted embryos, terminating pregnancies.”
The FDA and the Decision to Include the “Implantation Idea” on the Morning-After Pill’s Label
Despite the lack of scientific evidence, the Food and Drug Administration included information about the “implantation idea” on labels for emergency contraceptives. During the approval process for the drugs in 1999, the manufacturer of Plan B (Barr Pharmaceuticals, which has been acquired by Teva Pharmaceuticals), had asked the FDA not to include the implantation idea on it. But the FDA decided to because of hypotheses about how the pills worked:
Experts say implantation was likely placed on the label partly because daily birth control pills, some of which contain Plan B’s active ingredient, appear to alter the endometrium, the lining of the uterus into which fertilized eggs implant. Altering the endometrium has not been proven to interfere with implantation. But in any case, scientists say that unlike the accumulating doses of daily birth control pills, the one-shot dose in morning-after pills does not have time to affect the uterine lining.
“It takes time for an endometrium to change, for its cells to divide,” said Susan Wood, a biochemist who, shortly after Plan B’s approval became the F.D.A.’s top women’s health official and later resigned, frustrated with the delay in making the pill available without prescription.
“Wishful thinking” on the part of scientists also played a role, as some of them “thought that if it could also block implantation, it would be even better at preventing pregnancy.”
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