Heather Corinna replies:

Labels inside every box of morning-after pills, drugs widely used to prevent pregnancy after sex, say they may work by blocking fertilized eggs from implanting in a woman's uterus. Respected medical authorities, including the National Institutes of Health and the Mayo Clinic, have said the same thing on their websites.

Such descriptions have become kindling in the fiery debate over abortion and contraception. Based on the belief that a fertilized egg is a person, some religious groups and conservative politicians say disrupting a fertilized egg's ability to attach to the uterus is abortion, "the moral equivalent of homicide," as Dr. Donna Harrison, who directs research for the American Association of Pro-life Obstetricians and Gynecologists, put it. Mitt Romney recently called emergency contraceptives "abortive pills." And two former Republican presidential candidates, Newt Gingrich and Rick Santorum, have made similar statements.

But an examination by The New York Times has found that the federally approved labels and medical websites do not reflect what the science shows. Studies have not established that emergency contraceptive pills prevent fertilized eggs from implanting in the womb, leading scientists say. Rather, the pills delay ovulation, the release of eggs from ovaries that occurs before eggs are fertilized, and some pills also thicken cervical mucus so sperm have trouble swimming.

It turns out that the politically charged debate over morning-after pills and abortion is probably rooted in outdated or incorrect scientific guesses about how the pills work.

Read the rest of this story that's news-but-isn't at the Denver Post here.

Or, as we explained here a couple years back when we wrote our Birth Control Bingo page about EC:

Emergency contraception (EC) is a method of birth control, in that it is a means to prevent pregnancy before it occurs. Plan B can prevent pregnancy primarily, by delaying or inhibiting ovulation and inhibiting fertilization, and that may be the only way it works, as it is the way it has been proven to work in clinical studies. As explained by the ARHP, "although early studies indicated that alterations in the endometrium after treatment with the regimen might impair receptivity to implantation of a fertilized egg, more recent studies have found no such effects on the endometrium. Additional possible mechanisms include interference with corpus luteum function; thickening of the cervical mucus resulting in trapping of sperm; alterations in the tubal transport of sperm, egg, or embryo; and direct inhibition of fertilization. No clinical data exist regarding the last three possibilities.

Also, an important reminder about that "morning-after" moniker: emergency contraceptive pills can work for up to 120 hours, or five days after a possible or known pregnancy risk, not just the morning-after. They are most likely to be effective the sooner they are taken, ideally within 24 hours after a risk, but still can help substantially reduce the risk of unwanted pregnancy if taken within 120 hours.

Of course, when it comes to the politics of all of this, realistically, these facts likely won't change a thing for people who want to claim any kind of contraception is an abortifacient. It hasn't before, and probably won't now, either. In order for this to change anything for those folks, medical science would actually have to matter to them, and most typically, it doesn't.

We also think presenting the political opposition to EC as a mere factual misunderstanding is more than a little iffy, but when the opposition doesn't magically vanish with yet another try and getting these facts out there, facts that have already been out there for some time, that'll be apparent without us having to say anything else about it.

Cross-posted from our Tumblr here