You may have heard it referred to as "the morning after pill", as "Plan B", or by many other names. Call it what you like, but getting past the names, in this post I would like to investigate into the true nature of this famous pill with an unbiased and purely biology based stance. What does it do? How does it operate? What biological changes does it induce in the body? Does it prevent pregnancy or is it an abortifacient, i.e. does it induce an abortion?
Before I delve into the nature of Plan B, I would like to first like to introduce a perhaps more controversial pill, Mifiprex (mifiprestone/misoprostal). Note, first, that this pill is not synonymous with the Plan B pill (Levonorgestrel), but is in fact a different pill. (though it may have a similar effect on the female body)
Mifiprex blocks the hormone progesterone, which maintains the lining in the uterus. The lining is the site in where the blastocyst (200-300 cells) attaches and where it will continue to develop until birth. With progesterone production impeded by the drug, the uteran lining is shed and expelled through uteran contractions. The lost of the uteran lining makes it impossible for the blastocyst to attach to the uterus, and thus, it too is ultimately expelled.
Plan B, on the other hand, operates primarily by preventing ovulation, so that any sperm remaining in the body will be unable to fuse and create a zygote. This being said, studies have shown that Plan B can also sometimes cause the loss of the uteran lining, making it act in a similar fashion to Mifiprex.
Thus, we can say that Plan B carries with it the possibility of causing the loss of the uteran lining. However, the same can be said about Mifiprex, for although this drug carries with it a far greater likelihood of loss than Plan B, it is still not by any mean certain, for the drug often fails. Thus both pills, though not synonymous in chemical composition, can be thought of as functionally synonymous in their biological effects, for they both have the possibility to induce the same outcome.
Now, as to whether these drugs are abortifacients or not is based entirely on the definition of pregnancy, for abortion is the termination of pregnancy. If you consider pregnancy to begin once the blastocyst attaches to the uterus, as some individuals do, then these drugs would not be abortifacients, for they do not terminate pregnancy, but prevent it, even if the blastocyst is expelled. However, if your consider pregnancy to occur at conception, then both drugs are indeed abortifacients, for they prevent the blastocyst from attaching to the uterus, an thus terminate its development, and therefore its life.
