Both the IUS & the Cu-IUD are thought to work primarily through prevention of fertilisation, but the IUS seems to have more of an anti-implantation effect as part of its effectiveness than the Cu-IUD does.
Both are extremely effective, with the LNG-IUS being marginally more so. One prospective cohort study found the Pearl index to be 0.52 for the Cu-IUD and 0.06 for the IUS. The precise figures may well have been partly due to the IUS users being older overall (interesting; would have thought it would be the other way round) although adjusting for age still left the IUS coming out as more effective except in women aged 40 to 50 years.
The Mirena is licenced for 5 years for contraception, but may well be effective for longer; cumulative pregnancy rates have been found to be 1% at 5 years and 1.1% at 7 years. This may be partly due to a user effect, in that long-term users tend to a) be older and b) have a well-placed IUD. For endometrial protection it’s licenced for four years but has been found to be effective for up to five.
Cu-IUDs can be inserted at any time in the menstrual cycle if reasonably certain the woman is not pregnant; a review of eight studies found reasonable quality evidence that timing of insertion does not significantly effect risk of insertion pain, bleeding, expulsion, or pregnancy rates. If UPSI has occurred, insertion has to be within 120 hours of either the earliest UPSI that cycle or the earliest estimated date of ovulation.
LNG-IUS (Mirena or Jaydess) are licenced for insertion in the first seven days of the menstrual cycle. Insertion at other times is off-licence, but considered reasonable as long as it is reasonably certain the woman is not pregnant. ‘Reasonably certain’ is considered to include any of the criteria below:
- No intercourse since last normal period
- Correctly and consistently used reliable contraceptive method
- 1st 7 days of a cycle if period normal
- Within 7 days of a miscarriage or TOP
- Within 4 weeks of giving birth (but note UKMEC below)
- Within 6 months of giving birth if other LAM criteria met
- If 3 or more weeks since last UPSI and pregnancy test negative
It isn’t known quite how soon contraceptive protection is established and usual advice is 7 days; LNG-IUS should not be used as PCC. Precautions are not required when IUS inserted within 7 days of start of menstrual cycle or 7 days of TOP.
Note that all intrauterine methods are UKMEC 3 for insertion between 48 hrs and 4 weeks postpartum. Guidance on insertion in first 48 hours not yet available but will be included in the next UKMEC. (The Cu-IUDs are all WHOMEC1 in first 48 hours, and the LNG-IUS is also WHOMEC 1 in non-breastfeeding women in first 48 hours, but WHOMEC 3 in breastfeeding women for whole of the first four weeks. (Note that IUS is only licenced for insertion at 6/52 postpartum, so insertion between 4 and 6 weeks postpartum is fine under UKMEC but is still off-licence.) Insertion immediately after birth may be associated with higher expulsion rates, but more evidence is needed.
When fitting IUC post-surgical TOP, it should ideally be inserted at the end of the procedure. (This has been shown not to increase the risk of expulsion or of side-effects.) Post-medical abortion IUD can be fitted any time after passage of POC has been confirmed by clinical assessment or local protocols; remember need for additional precautions if IUS fitted after Day 7 post-abortion.
Switching from other contraceptive methods
When the method has been used correctly and consistently, thus putting the woman in the ‘reasonably certain not pregnant’ category:
With the Cu-IUD things are straightforward due to the post-coital effect. The only caution is that, if the switch is from an IUS to a Cu-IUD, then additional precautions are advised in the seven days before the switch, just in case there’s a problem with inserting the new method and it can’t be done.
With the IUS, the rule is to use extra precautions for seven days in any situation where ovulation may be occuring. This means:
- In days 2 – 6 of the PFW and first week of CHC cycle (this may be overcautious, but there’s a theoretical risk of ovulation occurring in this time; if inserted in weeks 2 or 3 of the CHC cycle, no extra precautions are needed)
- With the POP at any time
- If changing from an implant after its expiration date (changing over during the lifetime of the implant is fine; no overlap needed)
- If changing from DMPA 14 or more weeks after the date of the injection (changing during the time of the injection or up to two weeks later, again, is fine). For both this and the above, note that this only applies if the woman has used other methods/been abstinent during that time, or else she won’t be in the ‘reasonably certain not pregnant’ category!
- If changing from the Cu-IUD – and for this precautions or abstinence are also advised for 7/7 before the change
- Barrier methods if after day 7 of the menstrual cycle.
Insertion and PID risk
Women at risk of STI should offered screening when requesting IUC. ‘Risk of STI’ includes the following groups:
- Sexually active <25 yrs
- New sexual partner past 3/12
- >1 sexual partner in past year
- Regular sexual partner who has other sexual partners
- History of STIs
- Attendance as previous contact of STI
- Alcohol or substance abuse
Screening needs to include chlamydia at a minimum and can include gonorrhoea (it automatically does in our area, so that solves that one for me) but does not need to include an HVS. Suspected BV or candida should be treated but this should not delay IUC insertion.
You don’t, however, need to wait for the results before insertion, so it’s possible to screen and insert at the same time, as long as the woman is both asymptomatic and contactable (as she will need to be contacted and screened if the results are positive). If the woman is symptomatic, or at particularly high risk (such as a known infected partner), things get more complicated; the ideal in this case is to delay insertion until results are back, any infection treated, and symptoms resolved (with bridging contraception offered if necessary). However, emergency IUCD can still be considered, in which case it’s advisable to give antibiotic prophylaxis.
If a woman is diagnosed with STI, don’t forget to advise her to abstain until she and any current sexual partners have finished treatment, or for 1/52 post-treatment if single-dose azithromycin is used.
In case of PID with an IUD in situ, the IUD does not automatically need to be removed. Removal may help short-term outcomes but this isn’t clear.
Group A strep infection post-IUD insertion can, in rare cases, cause life-threatening septicaemia/toxic shock syndrome, so, although screening isn’t recommended, women found to be infected with vaginal GAS should be treated prior to insertion. Group B strep isn’t a problem with IUCD insertion and does not need treatment.
Routine prophylaxis in cases of increased endocarditis risk is not recommended.
Risks and benefits
Cu-IUD may be associated with reduced risk of endometrial and cervical cancer.
LNG-IUS seems to reduce primary dysmenorrhoea and pain associated with endometriosis/adenomyosis.
Both LNG-IUSs can reduce menstrual bleeding, but only the Mirena is officially licenced for this indication.
Hormonal side-effects (such as acne, breast pain, headaches and mood changes) can occur with the LNG-IUSs, but tend to decrease with time. Prevalence is between 1 and 10%.
Cu-IUDs and LNG-IUSs have both been associated with increasing weight gain, but this may be due to the confounder of increasing age, as no known causal mechanism is known.
Irregular bleeding typically improves by 3/12, but around 20% of women (with IUC generally) still have irregular bleeding one year after insertion. Postpartum insertion seems to be associated with prolonged bleeding (of similar heaviness) with Cu-IUD but shorter and lighter bleeding with LNG-IUS. An RCT found that neither mefenamic acid nor tranexamic acid helped with irregular bleeding with the LNG-IUS.
IUC does not affect bone mineral density.
Evidence is currently insufficient to say whether the LNG-IUS increases breast cancer risk or risk of recurrence.
Progestagen-only methods (all types) don’t seem to affect risk of MI or of VTE, but the evidence isn’t conclusive as yet and so specialist opinion is advised when considering POC for women with SLE, who are at increased risk of thrombosis. Note that if a woman has a cardiac condition that puts her at increased risk of vasovagal events, she may need to have her insertion performed in a hospital setting.
Expulsion happens in 1 in 20 women and is most common in the first year, most of all in the first three months of that year.
LNG-IUS increases the risk of functional ovarian cysts (risk between 1 and 10%) which can cause abdominal pain. These are not considered a reason to remove the IUS if the woman is happy with it, and a history of ovarian cysts is not a contraindication to insertion.
Pelvic pain may occur as a side-effect of either type of IUC; it seems to be more common with Cu-IUD than with IUS but the difference isn’t statistically significant.
Perforation risk is approximately 2/1000 and is about 6 times higher in breastfeeding women.
Cu-IUD use is a possible risk factor for recurrent candida, but unproven. It’s a definite risk factor for BV, and women with a Cu-IUD and recurrent BV (or recurrent candida) may wish to consider IUCD removal. It isn’t clear whether the IUS is a risk.
Another method of contraception should be used for 7 days before the removal of intrauterine contraception (including replacement, in case there are problems with reinsertion). The exception is Cu-IUDs removed in the first three days of the menstrual cycle.
Use outside licensed duration
Cu-IUDs with ≥300mm2 copper inserted after age 40 can be left in until the woman is postmenopausal (1 year after last period if >50, 2 years if <50). 52mg LNG-IUS inserted after 45 can likewise be left in until after the menopause if woman amenorrhoeic – otherwise, 7 years if inserted after the menopause.
If a woman <45 presents late for change of her 52mg LNG-IUS, the rule is that between 5 and 7 years she doesn’t have to wait three weeks for change if pregnancy test negative, but should still get a repeat pregnancy test three years later. If >7 years, she needs to take other precautions for three weeks and then get negative test. There is no such leeway on the 13.5 mg LNG-IUS; if a woman presents >3 years after insertion, she needs to wait for three weeks after last UPSI and get negative pregnancy test before replacement.
- c 2. c 3. a 4. d 5. c 6. d 7. d 8. a 9. b 10. d