The copper intrauterine device, or IUD, is one of the most effective methods of contraception. Have a doctor shove a T-shaped copper wire into your uterus and watch as you suddenly prove completely invulnerable to pregnancy! But when it comes to how the copper IUD actually works, without any hormones in it preventing pregnancy, most of us might not have a clue. It turns out that the mechanism that makes copper IUDs so effective is still kind of mysterious; but we do know it has to do with copper ions and how they interact with sperm as it enters the body.
But first, a little history: there's a thoroughly debunked story that the idea of the copper IUD originated with Arabian traders putting copper in their camels' uteruses, but it looks as if copper had its real entry into the world of commonly produced contraception in 1969. The Chilean physician Jaime Zipper began to add copper to intra-uterine devices, improving on a design by his colleague Howard Tatum at the Population Council which actually fitted properly into the uterus. Tatum's the one who came up with the idea of the T-shape we see on modern IUDs; before that, IUDs were in many coiled shapes, often looking slightly like children's graffiti. Case Western Reserve University's collection of pre-T IUDs will make your uterus contract.
If you're not particularly worried about how the copper IUD works in your body, only that it does work, be reassured: it's got an insanely good success rate. It's one of the most trustworthy contraceptives there is, and as we'll discuss, science indicates that it doesn't raise the risk of being poisoned by copper or damage your fertility in the future. If you are curious, though, and not satisfied by the perfunctory explanations of copper-as-sperm-killer at your gynecologist's office ("copper is toxic to sperm?" why?!), this is the article for you. But be warned, it does include some gory bits, like sperm tails falling off and rogue sperm being absorbed into your own cells. (Not to be read while being starry-eyed about pregnancy, that's all I'm saying.)
So this is the one thing you may not be told about the copper IUD: how copper toxicity actually works. Get ready for a slightly sticky, sperm-deadly ride.
Why Copper Is Massively Bad For Sperm
When it comes to contraception, copper has a bit of a mysterious effect. But the real aim of the copper IUD isn't the cervix, the ovaries, or our eggs: it's the sperm itself. Copper's a massively effective spermicide, and the sperm are killed off before they can fertilize anything and produce a case of the babies. But why is copper so rampantly toxic to sperm in particular without hurting any other parts of the reproductive system?
The IUD works by releasing copper ions, but they aren't going to migrate all over your body: a study of rats in 1972 found that putting copper in one "horn" of the uterus didn't affect the rest of it, indicating that copper isn't planning on escaping your reproductive organs. And it's the ions that cause the real trouble to sperm. A copper IUD's ions create a completely toxic environment to foreign bodies, including sperm; that environment prompts sperm phagocytosis, in which the sperm is killed and then "devoured" by other cells.
It's not all about direct attack, though. You'll remember from sexual health class that sperm look like miniature tadpoles, and have to "swim" to try to penetrate an egg. Copper ions seriously inhibit the ability of sperm to move, which is called their "motility". That effect carries all the way up into your fallopian tubes.
One of the most dramatic things copper does? It actually detaches the sperm from its tail. The UN's report on how the copper intra-uterine device works looked at sperm when they're affected by the copper IUD, and a majority of them had separated in half, head from tail. That's one hell of a way to make sure you don't get preggers.
How The Copper IUD Protects You From Pregnancy (Besides Killing Sperm)
It's not just that the copper IUD kills sperm, either. It looks like copper also alters the thickness of cervical mucus, making it harder for sperm to get through, which is how the hormonal IUD works too. But the level of copper in the mucus of the cervix also means that the sperm can't actually penetrate it.
Interestingly, copper IUDs, if inserted up to five days after unprotected sex, can operate as seriously effective emergency contraception, though frankly it's not necessarily the best idea unless you've already got an appointment scheduled.
Is Copper Safe?
You might be worried that a copper device in the body might result in copper toxicity, a nasty condition where copper (which is toxic to humans in large doses) causes all kinds of side effects. But studies have shown that the copper ion levels released by IUDs are actually tiny, and certainly not enough to do anything to human health. In fact, a 1980 study found there was no difference in bodily copper levels between people with copper IUDs and people without them.
Does Copper Affect Future Fertility?
Copper isn't just an effective sperm killer in ladies' bodies. A study of 232 infertile men in Iran found that all of them had high levels of copper in their bodies, meaning that copper might be a serious complicating factor for men's fertility. But it's important to note a few things. One is that there's no evidence that copper IUDs actually act as abortive mechanisms once a fertilized embryo is implanted (which is how a pregnancy starts). They're not going to stop a pregnancy if something slips through a net.
There's also, according to current studies, no sign that having an IUD will affect your future fertility if you decide to have it removed and try to get pregnant; a study in China found that nearly 80 percent of women who chose to have a copper IUD removed were able to get pregnant afterwards.
If you've heard that IUDs can cause infertility, that's actually a hangover from an earlier, now-banned form of intra-uterine device, the Dalkon Shield, that caused all kinds of havoc in the 1970s because it had a flaw that allowed bacteria to be introduced into the uterus. Don't worry; modern IUDs, including copper ones, don't have this flaw and don't have the same risks.
In fact, since copper IUDs are non-hormonal, you could theoretically get pregnant the same day you get it removed. And if that still sounds like a nightmare, the good news is, the copper IUD lasts up to 10 years.
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