The levonorgestrel intrauterine system (Mirena IUS) is a popular IUD. It contains the hormone levonorgestrel and over time many women gets lighter periods or even lose their periods altogether. This is a desirable side effect. The only problem is the promise of very light or no periods and combined with long acting reversible contraception comes with a price – many women have an initial bout of irregular spotting and/or bleeding. Unfortunately, many women are not adequately counseled about this possibility and as a result most women who get their Mirena removed for reasons other than wanting to get pregnant do so in the first 6 months and the most common reason cited is irregular bleeding.
Preventing early removal of the Mirena is important for the following reasons:
- Contain costs. IUDs themselves are expensive and there is often a co-payment for insertion as well.
- Prevent unplanned pregnancies. Long acting reversible contraception (LARC) is the most effective form of contraception because there is no user error, and so with the IUD out the next method chosen is likely to be less effective when considering real world experience. Not everyone has a plan for their post IUD contraception and that time of considering what to use next is very high risk for an unplanned pregnancy.
- Reduce the burden of complications. While significant complications with IUD insertion are very low (less than 1%), they are all associated with the insertion. If you have an IUD inserted and pulled out 3 months later you have assumed that risk for nothing.
The best way to prevent dissatisfaction related to a known side effect (irregular bleeding) is to be adequately counseled about that side effect. So how common is irregular bleeding after a Mirena IUS?
There are a couple of high quality studies to consider. These studies followed women after the insertion and they completed daily diaries to record bleeding, so the data is prospective (these were typically studies looking at ways to reduce post Mirena insertion irregular bleeding).
The average number of days with any bleeding in the first 90 days after Mirena insertion was 35 in one study (May 2013), but it ranged from 18-55. In another study (Sept 2011) the average number of bleeding days that required a pad or tampon in the first 84 days after insertion was 22-32 days, but 25% of women bled for 33-55 days (the longest was 64 days).
While the studies aren’t perfect (they varied slightly in how they quantified the bleeding) and the diaries were not collected by investigators daily, but rather batched and collected later, they do confirm that in the first 3 months after a Mirena is inserted there is a fair bit of spotting or bleeding. If you add the days together it totals about a month, but 50% of women will bleed more than that.
Bleeding for the equivalent or at least (and possibly more) than 1 month out of the first 3 in a random way is a nuisance. Studies tell us that overall its much less blood that a period, it’s just smaller amounts with an unpredictable pattern. However, this nuisance bleeding decreases significantly over time and is important to put in the big picture. If you look at all methods of reversible contraception (Mirena, copper IUD, pill, patch, depo-provera shot. ring, and implant) women with the Mirena IUS have the highest satisfaction scores at 1 year. Also, looking at all methods of birth control, women who chose a Mirena are more likely to be using that method at a year compared to women who chose a different method.
While you should be prepared for a fair bit of irregular bleeding in the first 3 months after your Mirena IUS is inserted (and if you are in the 50% who bleed for fewer than 30 days, then great!) you should also know that if you stick with it by 1 year you are more likely to be highly satisfied with your Mirena (and less likely to be pregnant) than if you had chosen a different method.