Plan B is not an abortifacient. Pass it on.
Plan B is widely opposed. Why? Well, if you’re a fundamentalist Christian, you might be under the impression that Plan B either prevents the implantation of a fertilized embryo (which you regard as a Human Life), or that it dislodges an implanted embryo.
The latter is certainly false. The former is almost certainly false as well.
A science blog explains. The full post has nice graphics and lots of detail, so I encourage you to go read it.
[Plan B] is a form of birth control that tells the woman’s ovaries to hold off on releasing any eggs for a short while. It’s called emergency contraception, because it is used by a woman who has, for whatever reason (rape, a broken condom, misplaced enthusiasm, second thoughts, anything) had unwanted sperm in her reproductive tract, and she wants to make sure that this isn’t the moment her ovaries happen to pop a follicle.
Plan B is not an abortion.
Plan B doesn’t help if one is already pregnant, and it doesn’t affect any implanted zygotes. Pregnant women produce progesterone naturally.
Straightforward enough, right?
Well, so why does the FDA material on Plan B say this?
3. How does Plan B work?
Plan B works like other birth control pills to prevent pregnancy. Plan B acts primarily by stopping the release of an egg from the ovary (ovulation). It may prevent the union of sperm and egg (fertilization). If fertilization does occur, Plan B may prevent a fertilized egg from attaching to the womb (implantation). If a fertilized egg is implanted prior to taking Plan B, Plan B will not work.
And why does the Canadian Physicians for Life group say this?
[Plan B] may prevent ovulation or, if fertilization has occurred, it may ruin the implantation of a newly conceived human being.
Everyone agrees that Plan B has no effect on an implanted embryo. But what about the possibility that it can prevent implantation?
Although it could possibly be the case that Plan B interferes with implantation, our best current evidence is that it does not. Since it’s pretty darn difficult to prove a negative, it’s misleading to go around saying that Plan B may prevent implantation.
This Population Council report has a summary of an animal study done by Reproductive physiologist Horacio B. Croxatto
of the Chilean Institute for Reproductive Medicine in Santiago, Chile:
The researchers found that levonorgestrel inhibited ovulation totally or partially, depending on the timing of treatment and the dose administered. However, the drug had no effect on fertilization or implantation when it was administered shortly before or after mating or before implantation.
(also available as HTML)
The American Academy of Family Physicans sums it up this way:
Some individuals may consider these hormones to be abortifacients if they interfere with implantation. However, the proven mechanisms of action consist of inhibiting or delaying ovulation. These hormones will not dislodge an implanted embryo.
Recent studies in rats and monkeys have shown that post-ovulatory use of ECPs do not have any effect on pregnancy rates. Studies in humans have shown that the rate of ovulation suppression is approximately equal to the effectiveness of emergency contraceptive pills, suggesting that might be the only mechanism by which they prevent pregnancy.
Because of the difficulty of studying pre-implanted embryos inside the uterus and fallopian tubes, both sides of this debate concede that completely proving or disproving the theory may be impossible.
It seems fair to conclude that our current best evidence is that Plan B does not interfere with implantation.
Why is this important? In a nutshell, it obviates any principled objection to Plan B from anti-abortionists. Even if you believe that human life begins at fertilization, which is a pretty extreme view to take in the first place, there is still no reasonable objection to Plan B being widely available, since all available data suggests that it does not interfere in any way with implantation.
And if you believe that human life begins at implantation, the case is even more open-and-shut. Plan B does not interfere with an implanted embryo. It never causes an “abortion”.
P.S.: Don’t confuse Plan B, an emergency contraceptive, with RU-486, a genuine abortifacient, which causes an emplanted embryo to be dislodged.