Before we even get started: The universally accepted definition of “pregnancy” within medical science begins at implantation — at the moment a fertilized egg adheres to the lining of the uterus. That’s when pregnancy begins. Not at ovulation, not at ejaculation, not when the winning sperm meets the egg and wriggles its way in. Implantation. So misguided people who insist that pregnancy begins at fertilization are just plain wrong. Right wrong. And to be sure, they have a right to be wrong. They just don’t have a right to dictate national policy based on their wrongness (or they didn’t used to, at least).
But what if you’re comfortable rejecting medical science out of hand and insisting that emergency birth control — the morning-after pill — is an abortifacient for preventing implantation? If, for instance, you’re a fundamentalist Christian who owns a crafts store and don’t want to support health insurance coverage for that form of birth control? If you’re haunted at night by the image of tiny little homunculi floating around in an empty uterus, bouncing off the razor wire-lined endometrium made so inhospitable by those evil birth control pills before being summarily flushed out of an uncaring womb?
Well, you’re still wrong. But that particular mistake is a little easier to make.
The common belief is that hormonal birth control, be it the standard pill or the more concentrated morning-after pill, prevents pregnancy three main ways:
1. Preventing ovulation. Progestin and estrogen block release of the hormones that would cause the ovarian follicles to grow and pop out an egg — in essence, they convince the ovary it’s already released an egg and doesn’t need to release another one.
2. Thickening cervical mucus. The mucus on and around the cervix, under the influence of the birth control pill, thickens enough to keep those little swimmers out of the uterus and fallopian tubes and away from any ova that may have escaped the ovary (as might happen if, for instance, the pill isn’t taken as directed).
3. Thinning the endometrium. When the lining of the uterus is thinned, a fertilized egg can’t implant and ends up getting flushed out of the body, except this third bullet is wrong.
(Yeah, I really wanted to hold out for a clever tease-and-reveal there, but the chance that that list would get passed around out of context as a list of ways the pill really does prevent pregnancy is pretty good. I’m sacrificing snark for accuracy here, people.)
Yes, a steady diet of estrogen and/or progestin, as one would receive through consistent use of birth control pills or rings or patches or what have you, does result in a thinner uterine lining. Emergency contraception, of course, being (in essence) that same kind of medication in two hefty doses, doesn’t have this effect. So why does your Plan B pill pack say it might? Why does the Mayo Clinic’s Web site say it might? Why does the Mayo Clinic’s Web site say it might even when their own doctors say it’s not the case?
Teva Pharmaceuticals, current makers of Plan B, couldn’t tell you. Original manufacturers Barr Pharmaceuticals (since acquired by Teva) asked in writing back in 1999 that the FDA change its labeling because it was, in fact, misleading. The old labeling was based on Plan B’s active ingredient, a synthetic progesterone, and the ways in which it could theoretically prevent pregnancy. And it’s that theoretically that’s the problem. See, one of the strengths and weaknesses of science is that you can’t rightly leave out information in the interest of making things less confusing, and the possibility that a progesterone-pushing pill could prevent implantation does, in fact, exist. It can’t be ruled out, because you can’t prove a negative — it just isn’t supported by any scientific evidence. At all.
In 2002, tests failed to provide evidence that Plan B prevented implantation. In 2005, when the FDA was considering Plan B for over-the-counter availability, the makers once again asked that the implantation warning be removed from the pack. But Steven Galson, head of the FDA’s Center for Drug Evaluation and Research, said that studies couldn’t rule out the possibility of Plan B prevention implantation “in a small percentage of women,” and there you have it. Repeated and numerous tests since have shown not a lick of evidence that Plan B, or the similar emergency contraceptive Ella, actually prevent implantation, but because, by the rules of propositional logic, can’t prove beyond a shadow of a doubt that they don’t prevent it, the inaccurate labeling stays. Behold the scientific method, hamstrung by its own precision.
And so it stays on your pill pack, and on Web sites that know better. Without the ability to say, “Yes, unequivocally, we are absolutely, for sure, 100-percent certain that emergency contraception doesn’t prevent implantation, any more than we are 100-percent certain that gravity will keep you pinned to the earth,” we’re stuck with 1960s-era drug labels from a time when medical science wasn’t absolutely sure how the Pill worked, but had a pretty good idea, and that the uterine lining thing sounded like a reasonable possibility, one supposes. But put it out there, and people are going to grab onto it, either as a result of not understanding science or as a bad-faith effort to protect the poor blastocysts from the evil, slutty, hateful feminists — as much as you’d think the anti-choice movement would be all over the discovery that Plan B doesn’t endanger free-floating blastocysts in the slightest.
Additional fun facts, for those who enjoy fun facts: It’s not even thoroughly established that the endometrium-thinning effect of traditional birth control pills and similar hormonal methods prevents implantation. (Any woman who’s gotten pregnant while on the Pill can probably give her opinion of that.) While it certainly sounds reasonable to assume a blastocyst would have a harder time digging into a thinner, less cushy and inviting endometrium, several older but still noteworthy studies call it into question. In 1999, the American College of Obstetrics and Gynecology felt that that
“No direct evidence exists showing that implantation is prevented by progestin-only methods” and “The evidence does not support the theory that the usual mechanism of action of IUDs is destruction of the uterus,” say the authors. After reviewing all the research available on the modes of action of all contraceptives in question the authors summarize their reports by explaining that “Even though the precise mechanism of action of modern contraception is not yet fully known, scientific evidence suggests the main mechanisms of action for each method. Inhibition of ovulation and effects on the cervical mucus are the primary mechanisms of the contraceptive action of hormonal methods. Evidence indicates that the primary mechanism of action of IUDs is the prevention of fertilization.”
“All of these methods, directly or indirectly, have effects on the endometrium [the lining of the uterus] that might prevent implantation of a fertilized ovum,” the researchers acknowledge. But they quickly point out, “So far, no scientific evidence has been published supporting this possibility.”
And at that same time, the American Association of Pro-Life Obstetricians and Gynecologists, which is an actual thing, said that “there is no direct evidence in the literature to support the third proposed method of action” (the “hostile uterus” theory) and that “the existing evidence indicates that ‘on pill’ conceptions are handled by the reproductive system with the same results seen with ‘off pill’ conceptions.” Though hormonal birth control does thin the endometrium, they agree, that doesn’t automatically impede implantation.
Not loving the dusty studies? As recently as 2011, the researchers behind Contraceptive Technologies were convinced that
When the two primary mechanisms [of combined oral contraceptives] fail, the fact that pregnancy occurs despite the endometrial changes demonstrates that those endometrial changes do not significantly contribute to the pill’s mechanism of action.
At the risk of repetition: It’s not like impeding implantation is the same thing as abortion anyway. Because pregnancy doesn’t begin a fertilization. Because believing something scientifically inaccurate doesn’t make it so. (Or at least, it didn’t used to.) But we, pro- and anti-choice alike, should all be wiling to agree that anything that prevents the creation of unwelcome embryos should be a good thing. So any time people want to start getting honest and accurate about birth control, actual, non-rubbish, non-religiously dictated, real science is ready to go. Just say the word, which, for the record, isn’t “impedes” or “implantation.”