"The Pill as an Abortifacient": Appendix A, on IUDs

It has come to my attention that my previous post on the Pill as an abortifacient may have been a little narrow. Certainly the Pill is the most common of the chemical contraceptives, but I would be remiss if I didn't include a section on hormonal IUDs (or Intra-Uterine Devices, like Mirena), another commonly misunderstood form of chemical contraception.


Many women are under the impression that an IUD is simply an implantable, more permanent version of the Pill. Well, semi-permanent anyway - they can usually be implanted and left for up to 5 years. The misconception there is that the chemical composition of an IUD is distinct from that of the common Pill, in that IUDs release only progestins while most common oral contraceptives contain both estrogen and a progestin (there are "progestin-only oral contraceptives", but these are usually prescribed for specific medical reasons related to gynecological health and are not the same as the estrogen-progestin oral contraceptives commonly referred to as "the Pill"). The role of progestins in contraceptive devices is two-fold as you may remember from the main post:

1. They thicken the cervical fluid to help prevent the entrance of sperm into the cervix and shorten its lifespan within the female reproductive tract, and
2. They dramatically thin the lining of the uterine wall that normally builds up and sheds cyclically in preparation for physical implantation and nutritional support of a fertilized embryo, making it very difficult for a fertilized embryo to implant successfully - it is instead "washed out" with the monthly menstrual flow. 

Unrelated to the hormonal effects of progestin, the IUD also attempts to physically interfere with entry of the sperm into the fallopian tube by its placement location (though the IUD can and will shift over time, and we're talking about microscopic sperm and eggs that would have to squeeze by... take that for what it's worth).

You may also recall from the main post on this issue that it is the estrogen component of oral contraceptives that prevents follicle maturation and ovulation from occurring monthly. Directly from the Mirena (a popular brand name IUD) website, this means that an IUD "may stop the release of your egg from your ovary, but this is not the way it works in most cases" (emphasis mine). 

What does it all mean, in practical terms, for IUD users? It means that you can assume that during most months, you will ovulate. Given the disruption of the normal cyclical patterns of progesterone circulation induced by the IUD, your normal fertility signs will also be disrupted (such as patterns in basal body temperature and cervical fluid consistency, which could normally be used to determine when ovulation is occurring). Bottom line: you have little hope of being able to determine when or if you've ovulated. At this point, all that's standing between your egg and fertilization is the thickened cervical fluid and the rather weak "physical barrier" of the IUD itself to sperm travel. 

Here in lies the main difference between the Pill and IUDs, as far as abortifacient properties are concerned: the IUD does comparatively little to prevent fertilization (relative to the Pill, which is designed to prevent ovulation altogether, however imperfectly that may work). Once a successful fertilization has occurred, you (as an IUD user) are now relying on the IUD to ensure that your body rejects that conception (as a result of the thinned uterine lining). If you happen to be a woman who is pro-life and defines life as beginning at conception, you have put yourself in a terrible position. You are using a birth control method that allows for ovulation to occur, and loosely attempts to prevent fertilization, but primarily functions to create an inhospitable uterine environment that will reject a fertilized egg. 

I won't venture to call one chemical contraception method "worse" than the other, because that really isn't the point here - that would be splitting hairs. I make this point because many IUD users may not fully understand the mechanism behind their chosen form of birth control (I've mentioned how I feel about the tragic dearth of patient education going on in OB/GYN offices these days) - they may believe, as most women on the Pill do, that they are not ovulating. Pro-life IUD users really need this information, so that they may carefully consider the facts: that they most likely are ovulating, and are therefore risking a lot of fertilization. It is precisely this risk of fertilization that lends chemical contraceptives their classification as "abortifacients".