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Study shows Mirena (LNG-IUS 52mg) significantly more effective than copper IUD in preventing pregnancy

A study, published online in the journal of Contraception, concludes that while both Mirena and copper (Cu-IUD) are highly effective methods – with Pearl Indices of 0.06 (95% CI: 0.04-0.09) and 0.52 (95%: 0.42-0.64) respectively – rates of contraceptive failure were increased eight-fold among those using the Cu-IUD versus Mirena (5.2 pregnancies per 1,000 women v. 0.6 pregnancies per 1,000 women).i The data also confirms low rates of in women, with a risk of around 1 per 1,000 insertions – and no clinically important differences between the two methods.ii

The study, called the European Active Surveillance Study for Intrauterine Devices (EURAS-IUD), comprised over 61,000 women from six countries, including the UK making it the largest to date to document contraceptive efficacy, adverse events and potential risk factors for uterine perforation among IUC use.

“This is a large study, conducted in a real world setting, which shows that both types of IUC are effective options for women, with a more favourable benefit-risk profile towards Mirena than the Cu-IUD,” said Dr Dearbhla Hull, Head of Medical Advisory, Women’s Health, Bayer HealthCare. “Many women are often unaware of the different contraceptive options available to them. It is important that, as part of any contraceptive consultation, all methods including IUC – which are among the most effective reversible methods – are discussed to ensure women are making informed decisions about the best method for their needs.”

EURAS-IUD also highlighted low absolute rates of ectopic pregnancy in women and explored the risk factors associated with perforation. Of the 118 total pregnancies, 21 were ectopic (7 in the Mirena group and 14 in the Cu-IUD group (95% CI: 0.10-0.66)). Eighty-one cases of uterine perforation occurred, accounting for 1.4 per 1,000 Mirena insertions (95% CI: 1.1-1.8) and 1.1 per 1,000 Cu-IUD insertions (95% CI: 0.7-1.7), a difference not considered statistically significant. Sixty-three of the total 81 perforations were associated with previously suspected risk factors including breastfeeding and time since last delivery ? 36 weeks. No perforations led to serious illness or to injury of intra-abdominal or pelvic structures.

While absolute rates of perforation and ectopic pregnancy in women are low, they may impact future fertility so benefits and risk of use should be carefully evaluated and insertion should be carried out in line with the summary of product characteristics for each method.


[i] Heinemann, K, et al. (2015) Comparative contraceptive effectiveness of levonorgestrel-releasing and copper intrauterine devices: the European Active Surveillance Study for Intrauterine Devices, Contraception, DOI: 10.1016/j.contraception.2015.01.011, published online 16 January 2015.

[ii] Heinemann, K, et al. (2015) Risk of uterine perforation with levonorgestrel-releasing and copper intrauterine devices in the European Active Surveillance Study on Intrauterine Devices, Contraception, DOI: 10.1016/j.contraception.2015.01.007, published online 16 January 2015.

Source: Bayer HealthCare