Outside of sterilisation, the IUD is the most effective type of contraception – and unlike a pill or condom, you can ‘set it and forget it’. So why is it used by only a minority of women?

“The

What closely resembles an alien insect and decapitates sperm? If you answered the ‘coil’, otherwise known as the intrauterine device (IUD), congratulations! You’re correct.

About the length of a paperclip, these bizarre objects come in a wide range of shapes, from frilly ovals to four-legged spiders. However, the most common variety in the Western world consists of a T-shaped piece of plastic with a dangling ‘tail’ of threads.

To work, IUDs must be placed inside the womb, where they can remain – depending on the brand and type – for up to 12 years. They’re incredibly good at preventing pregnancy.

In Asia, 27% of women use an IUD for contraception; in North America, 6.1% 

In fact, they’re the most effective contraception on the planet – aside from sterilisation or avoiding sex altogether. And apart from those options, they’re also the most popular birth control method worldwide. But that doesn’t mean that most women in every country have heard of them. In Asia, for example, 27% of women use an IUD for contraception. But the rate is just 6.1% in North America… and less than 2% in Australia and New Zealand.

Why is this? And why should more of us know about them?

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One reason IUDs aren’t more widely used in the United States might be the lack of marketing. Over the years, pharmaceutical giants have chosen to invest heavily in promoting the contraceptive pill instead, which is more profitable.

“I think patients now are more aware than they were in the past,” says Alyssa Dweck, a gynaecologist based in New York. “But money is obviously important.”

“There are many companies, with many different formulations [of contraceptive pill], with some of the differences hardly noticeable to individuals,” says David Hubacher, an epidemiologist at the non-profit human development organisation FHI 360. “In contrast, if you look at the main IUD we’ve had on the market since 1988, ParaGard, there hasn’t been much advertising.”

Another reason is that they have a bit of an image problem. There are plenty of hostile rumours about IUDs out there – like the idea that they’re painful, cause infertility, or lead to bad sex. In the light of their checkered history, this isn’t particularly surprising.

The idea that placing a foreign object in a woman’s reproductive organs could prevent pregnancy first emerged in the late 19th Century. To begin with, doctors were pretty much just placing random objects in the cervix, the entrance of the uterus, and hoping that this would do the trick. These early precursors to the IUD, called “stem pessaries”, were made from all kinds of materials, such as bone and cat guts. But later versions were mostly metal screws with long, forked ‘tails’.

The first mainstream IUDs emerged several decades later, in the 1920s. These were popularised by a German doctor Ernst Grafenberg, who is better known today for having the ‘G spot’ named after him. 

Grafenberg’s design was a simple ring of metal that was placed in the womb, and he soon began performing scientific studies to see if they actually worked. All was going well, but their development was cut short when the Nazis arrested him. He was later rescued by the queen of birth control, Margaret Sanger, and fled to the United States. 

From then onwards, IUDs really took off. In China, IUDs were an important tool for implementing the one-child policy, along with forced sterilisations. To this day, the country has its own devices which have been especially designed or altered to make them more difficult to remove; they often require surgery.

In America, meanwhile, there was the Dalkon Shield disaster. This infamous brand, which had a broad ‘shell’ a bit like a horseshoe crab's, was introduced in the 1960s. They were based on the idea that IUDs with a larger surface area would be more effective. Instead, they had an unacceptably high risk of pregnancy. Even worse, they also led to widespread infections and infertility. It was a massive public scandal and more than 50,000 women ultimately filed successful lawsuits against the manufacturer.

“Women are always going to be concerned about their future fertility. It took a long time to make IUDs in a way that was considered safer, and to reorient women’s views,” says Dweck.

Luckily, modern versions are quite different. There are two main types: those that contain copper, and those that slowly release a low dose of the hormone levonorgestrel.

“The products we have today are very safe and effective,” says Hubacher. He points out that even when IUD use was at an all-time low, IUDs were five times more popular with female doctors than the general public. “And if you just look at the subset who were OB-GYN [specialists in reproductive medicine], the rates were up to nine times higher.”

To get to grips with this enthusiasm, it helps to compare them to other contraceptives.

If you take the pill the human way, over 10 years you have a 61% chance of getting pregnant 

Millions of women across the globe, from Melbourne to Mumbai, woke up this morning and punched a small pill out of its packet. They must remember to take one nearly every day, which is surprisingly difficult.

Theoretically, the combined contraceptive pill gives women less than a 1% chance of becoming pregnant in any given year. In reality, most of us accidentally miss around five pills each month – so the rate of pregnancy is actually more like 9%. That means that if you take the pill the human way for 10 years, you have a 61% chance of getting pregnant overall. In other words, more likely than not, you will get pregnant. (Find out more about the pill in our recent stories on eight women's stories of side effects and the 'masculinising' effect it can have on women's brains).

By one estimate, reliance on oral contraceptives leads to 960,000 pregnancies every year. There are also side effects, such as an increased risk of potentially life-changing blood clots and a faded sense of wellbeing.

The issue of compliance is common to most contraception, from condoms to the contraceptive patch. Human nature (and sexual behaviour) being what it is, these just aren’t used in real life as they are intended.

But IUDs are different. Because they require no maintenance aside from insertion, which is done by a medical professional, they’re exactly as effective as they say on the packet. Copper IUDs give women roughly a 1% chance of getting pregnant each year, which works out as an 8% risk over 10 years; hormonal versions provide less than a 1% chance each year or a 2% chance over a decade. The hormonal version comes with what many women see as an added bonus – one in five users find that their periods stop altogether.

Anna Foley, from New Zealand, decided to get a hormonal IUD a few years ago. “In general for me, I loved it because I always sucked at remembering to take the pill,” she says. “Plus I found that I had some negative side effects to the hormones, while the Mirena [IUD] had a lower dose.”

People used to think that IUDs mainly worked after conception, by making it impossible for a fertilised egg to implant. But experts no longer believe this to be the case.

Instead, IUDs work for two reasons. The first is that any object in the womb leads to an inflammatory response: a certain type of white blood cells rushes to the area, where they eat sperm and produce waste that is toxic to sperm. One study found that IUDs increased the number of these cells in the womb by 1,000%.

The second reason depends on the type of IUD. Hormonal versions modify a woman’s body to make it more difficult for sperm to reach a woman’s egg, and make her womb inhospitable in case one is fertilised. Copper IUDS, on the other hand, are fearsome sperm killers. As copper ions dissolve into the womb, they paralyse and even decapitate sperm – though exactly how remains a mystery.

Still, even modern IUDs come with some risks. The most serious is the possibility the device will be pushed through the wall of the uterus while it’s being inserted, which is classed as a medical emergency but only happens very rarely (one in every 1,000 insertions). There is also a slight increase in the risk of infections, pelvic inflammatory disease and of ectopic pregnancy among other things, but these disappear once it is removed. Of course, other methods of contraception come with risks too – roughly one in every 1,176 women on the pill are at risk of developing a blood clot in any given year, for example.

In terms of the intensity of the pain, I would have told you it was a 10/10 – Anna Foley

But one major concern many women have is that having an IUD inserted will be painful. And while this isn’t always the case, it certainly can be. Foley doesn’t mince words about her own experience. “In terms of the intensity of the pain, I would have told you it was a 10/10. It was really, really bad. And whenever I thought about the pain for the rest of the day I’d just start crying.”

Generally the most intense pain goes away within minutes – it’s like a fleeting spasm – and women are left with a dull ache for the rest of the day. And as several women have pointed out, it’s much less painful than one possible alternative: childbirth.

In fact, for years doctors thought that the pain of inserting an IUD would only be bearable for women who had already given birth, because their birth canals would be slightly stretched. This had an unfortunate effect: for years, many women didn’t hear about this method from their doctors. We now know that it doesn’t make a lot of difference – women who have already given birth tend to rate their pain as a “level four”, as opposed to a “level six”.

Many doctors are now arguing that all women should be given the option of having a local anaesthetic before insertion, in the hope that this will increase the number of women getting IUDs. Regardless, the popularity of these ingenious, sperm-slaying devices has been increasing steadily since the 2000s. “There’s a big push to recommend IUDs as a first-line option,” says Dweck. Though they’re expensive to buy and insert, over, say, a 10-year lifespan, they can be more cost effective than birth control pills – and health providers have caught on.

Who knows – maybe articles about how they exist will soon be redundant.

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This story is part of the Health Gap, a special series about how men and women experience the medical system – and their own health – in starkly different ways.

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