AHQ: How Does the Copper IUD Work?
Allie Has Questions is a new column where Greta answers any questions you have. Read more about the origins of the column here, and read past posts here. Do you have a question you want answered? Submit your question at this link, and you could be Allie for a post.
Dear Greta,
How does the copper IUD work?
Love,
Allie
Dear Allie,
I’m assuming you’re asking this already knowing how hormonal IUDs work, but here’s a refresher regardless: Hormonal IUDs release low doses of progestin into the body over time (between 3 and 7 years depending on which hormonal IUD you get). The primary effect is to increase the amount of cervical mucus, which stops semen from reaching the uterus, and other effects include halting ovulation and decreasing endometrial lining. In other words, the hormonal IUD blocks sperm from ever reaching an egg, but also makes it less likely for an egg to be released, and creates an inhospitable environment for the egg to implant.
Now that I’ve done the important work of answering a question you didn’t ask, I guess we can move on to the one you did. There’s only one type of copper IUD distributed in the United States, the Paragard IUD, so you would assume figuring out precisely how it works would be easy. Nearly everywhere, including the official Paragard website, will tell you that the copper IUD “kills sperm” or “blocks sperm from fertilizing an egg.” This is true, but it also does nothing to describe the mechanism behind these acts (very frustrating [very frustrating for me]).
Here’s the more in-depth description of how the copper IUD works:
The copper IUD functions primarily by releasing copper ions into the body over time. As the hormonal IUD does, the copper IUD thickens the cervical mucus, which acts as a physical barrier to the uterus. However, it also increases the levels of copper ions in the cervical mucus, which then acts as a spermicide to the sperm that manage to make it through. The ions both affect the sperm’s motility (the ability for them to move of their own accord, as opposed to mobility, or the ability for something to be moved. I learned the distinction for this response), and can break the head of the sperm from the tail. The main takeaway here is that sperm are quite weak.
A secondary aspect of the copper IUD is that it registers as a foreign object in the uterus, which prompts a bodily response that also functions to thwart contraception. The foreign object effect also exists with the hormonal IUDs, but its effect is proportional to size, and the copper IUD is much larger. The uterus becomes slightly inflamed after the insertion of an IUD, and releases white blood cells and prostaglandins, a group of lipids that attend to inflammation. The white blood cells target sperm, because they are on a mission to eradicate all foreign objects. Some studies suggest that the foreign body effect also affects implantation.
What’s interesting is that the same thing that makes the copper IUD so effective––releasing copper ions into the body––is the same thing that increases side effects, like cramps and stronger periods. Also, on the theme of things I found interesting while reading about this: the copper IUD does not halt ovulation, while the hormonal IUD usually does.
So, in short, the copper IUD kills sperm by releasing copper ions slowly over a long period of time into the body, which thickens the cervical mucus, tears sperm apart, and makes it so the sperm can’t move on their own. It also attacks sperm with white blood cells and might decrease the likelihood of implantation, but neither of those is the primary function.
The end!
Love,
Greta