What's the difference between an IUD and an IUS?

Mainly one has hormones and the other doesn't.

The IUD is made of copper, which has a toxic kryptonite-like effect on sperm, zapping them before they get to meet your egg. It also thins the lining of your womb so if a Roger-the-Dodger type swimmer does manage to hoodwink its way into an egg, it won't be able to embed.

The IUS, commonly known as the Mirena, slowly releases the hormone progesterone directly into your womb. This prevents the creation of potential new people by thickening the mucus in your cervix so sperm can't get through, as well as making your womb an unwelcome habitat for eggs. It can also stop your ovaries releasing eggs entirely.

Does the coil make my periods worse?

Potentially. Annoying, we know. But, again, it depends on which coil you choose.

The IUD can give you heavier and longer periods and isn't recommended for women who already experience heavy periods of doom.

The IUS has the opposite effect. It makes periods much lighter, and in some cases can stop them altogether. Although this might not be as amazing as it sounds if you're a worrywart who likes using your period as a not-pregnant reassurance device.

What exactly happens when a coil is inserted?

First things first, you will have to show the nurse your fanny. No, it can't be done through clothes. Lying down on a table, you will need to take your knickers off and open your legs. This can be a daunting experience if you've never had a smear test or STI test before, and if the thought really upsets you, it might be worth looking at other contraceptive options.

A speculum covered in lubricant (thankfully) will be inserted to open up the walls of your vagina so your doctor can get a nice clear view of your cervix. An anaesthetic gel or injection will be given and you will have to wait a minute or two for it to take hold. The T-shaped coil is then folded up and pushed through your vagina up into the cervix. This will hurt or be uncomfortable but it only lasts a few seconds. And that's it. All done. But expect some period-like cramping for a day or two afterwards.

Jane*, 24, had a copper coil inserted a year ago. She says: "I wouldn't say it hurt, it was more uncomfortable. Being injected was probably the most painful part but it just felt like bad period cramps. When the coil was actually being put in, it felt a bit like someone was pushing down on me or knocking the wind out of me but the anaesthetic helped. On a scale of one to 10, I'd probably rate the pain at seven. "

Can my boyfriend feel the coil during sex?

Nope. Not even if he has the largest penis ever to grace this earth. The coil sits in your cervix, not in your vagina, so even a penis resembling Mr Tickle's arm won't be able to navigate that far up. However, he may be able to feel the thin wire strings that hang down from the device into your vagina. These they might be a tad sharp so go slow on your first post-coil coital session. If he can feel them and it's uncomfortable, ask your doctor to trim the strings shorter.

Can the coil get dislodged during a particularly aggressive sex session?

Again, no. Simply because no penis can reach up that high. So bang away. In rare cases it is possible for a coil to fall out of its own accord, but never as the result of a "faster-harder-deeper" sesh.

Does the coil affect fertility?

Here's the thing. The coil doesn't affect your fertility. But Chlamydia does. It can cause a pelvic infection that scars your fallopian tubes. And what many people don't know is that Chlamydia can climb. Think of your vagina as Mount Everest, your cervix is the summit, and Chlamydia as determined to reach the top. The problem with the coil is it has two dangling strings offering the perfect leg-up to the danger zone. Although contracting Chlamydia when you are on the pill or another form of contraception is still bad news, the coil makes the whole fertility-destroying process much quicker. So please please, keep using a condom with any new partner.

Does the coil cause abortion?

OK. We're getting into morally murky waters here depending on when you personally believe a human life begins. But technically, no - the coil doesn't cause abortion. But if you believe life begins the moment a sperm meets an egg, then your view may differ.  Legally and scientifically speaking, pregnancy begins when a fertilised egg implants in the lining of the womb. This happens about 10-12 days after sex. Naturally lots of eggs don't implant anyway, so the coil is just giving this process a helping hand. The IUD and IUS prevent a fertilised egg from embedding by thinning the womb lining.

I've not had children yet. Can I still get a coil fitted?

Yes you can. Don't believe anyone who says otherwise. The idea only mothers can have a coil fitted is an old-fashioned view even some health professionals are guilty of reinforcing. Your vagina is big enough - even if you've not squeezed a baby out of it just yet. But there can be a reluctance to fit younger women with coils as, rightly or wrongly, some doctors may make age-based judgements on their safe sex practises. It is your right, and ultimately your responsibility, to choose a contraception that best suits your life. Just make sure you prove any judgemental health professionals wrong by always using condoms with new partners.

Can the coil get stuck inside me?

This is along the same lines of worrying whether a tampon can get lost inside you. And the answer is the same. No - because it has nowhere to go. The coil isn't suddenly going to break loose and start frolicking around your liver, brain, or foot. It's physically impossible. But during insertion there is a very small risk of perforation where the coil can get pushed through the wall of your womb or cervix. This only happens in a teeny tiny number of incidents, but it's best to go to a family planning clinic that spends all day every day inserting coils if you're nervous.

Thank you to the Family Planning Association for their help with this article.

Updated: 24/03/2011

Holly Thompson