They use either the hormone progestogen or copper to prevent pregnancy, as both repel sperm and prevent it from reaching the egg. Both are suitable for women aged anywhere from their teens to around the age of 55 or menopause.

One advantage of the copper IUD is that it doesn’t cause any hormonal side effects. Inserting an IUD is typically a “simple, safe procedure” according to Health New Zealand, while removing an IUD may briefly cause pain.

While rare, an IUD becoming embedded is more common with the hormonal IUD, while the threads breaking is more common with the copper IUD, possibly due to the difference in the material used.

What are the risks?

Should you be worried that your IUD could be embedded in your uterus?

Sexual Wellbeing Aotearoa (formerly Family Planning) medical director Beth Messenger says that this only happens in about 1 in 1000 IUD insertions.

In rare cases, the IUD can perforate the uterus completely, piercing all the way through rather than just getting embedded in the wall.

Do these complications reduce an IUD’s effectiveness? “We don’t really know how much that might reduce the contraceptive effect. So we would tend to tell people that it probably isn’t going to work, even though it might,” Messenger says.

The strings can sometimes “curl up” into the uterus, meaning “sometimes we can’t see the threads even when the IUD has been correctly placed”.

While it’s not routine to offer anaesthetic for an IUD insertion or removal, Messenger notes “the experience of pain is enormously varied”.

“Some women actually don’t really feel very much, but some will. If they’ve had a very painful past experience, then it’s probably appropriate to offer them an anaesthetic right from the start.”

As with any medical procedure, there’s the risk of infection. There’s a chance they can fall out, and they’re sometimes difficult to insert depending where the patient is in their menstrual cycle. If you get pregnant with an IUD in, there’s a chance it could be an ectopic pregnancy, forming in your fallopian tube.

Messenger says it’s important to note that IUDs are more commonly used than ever, so while it may seem that a disproportionate number of complications are occurring, that’s not necessarily the case. “It’s just that more people have them [IUDs].”

What are the benefits of having an IUD?

An IUD can also affect your period, for better or worse.

“The copper IUD tends to make periods heavier or more painful and then the hormonal IUDS can cause more irregular bleeding. The Mirena tends to make them lighter or even stop completely,” Messenger says.

Some advantages of an IUD or an implant are that they’re reversible and they start working from the moment they’re inserted and stop as soon as they’re removed.

“They are very effective forms of contraception, and they’re partly very effective because you don’t have to do anything with it once it’s in. It’s just working, it’s doing its thing, so you don’t have to think about it every day,” Messenger says.

She says it’s important to know how effective each method is and how they work, because one option that’s acceptable to one woman might not be acceptable to another, depending on their viewpoints.

“When making a decision about any treatment, and definitely with contraception, you need to know the good and the bad, and there is no perfect form of contraception.”

What you need to know about IUDs, according to a gynaecologist

Dr Guy Gudex, a gynaecologist and fertility doctor at Auckland Gynaecology Group and Repromed, says if you’re considering whether to get an IUD, it’s best to talk to a doctor who has experience with inserting them. He advises seeing a gynaecologist or going to a clinic such as Sexual Wellbeing Aotearoa.

“GPs increasingly have less and less experience putting IUDs in, unless they’re a GP with an extra or special interest in women’s health,” he tells the Herald.

Gudex says the risk of your IUD getting embedded in or perforating your uterus is “relatively low”.

“People are certainly warned, when they’re being counselled about whether or not IUDs are right for them, about that risk.

“Being difficult to remove and the strings breaking, that may or may not mean that it’s just a bit embedded in the wall. More often than not, it doesn’t mean that it’s embedded.”

Women who experience those complications won’t generally be covered by their health insurance, he says.

“Generally speaking, private health insurance won’t cover putting in an IUD if it’s just for contraception, and that means that if there is then a complication, say someone has private health insurance and they’ve got a problem with their copper IUD, then it won’t be covered.

“If people haven’t got private health insurance, they could get their IUD removed through the public system, but as you know, depending on where you live, there could be delays to that. And if you’re wanting it removed because you want to get pregnant, waiting for six months to have it removed could be pretty frustrating.”