Chance of pregnancy with IUD?
October 5, 2012 5:33 PM   Subscribe

How likely is it that I'll get pregnant with a Mirena IUD and no condom?

After consulting with my gynecologist and doing my due diligence on AskMe (thanks!), I had a Mirena IUD inserted 2 weeks ago. Yay! I'm still somewhat apprehensive about having sex with my boyfriend with no condom, however, for fear of pregnancy. [He is supportive either way.] We are monogamous, have been dating for 2+ years, and have both been tested for STDs, so we're only using condoms to prevent pregnancy. We previously used both hormonal birth control and condoms. I've done my research and know how much more effective IUDs are supposed to be than any other firm of birth control. Still, I keep coming across stories, both on Metafilter and the internet generally, of people getting pregnant with an IUD. I can't find any reputable research or authority specifically stating that a condom is unnecessary or gives any added benefit when you have an IUD.

Please give me your facts, advice, or anecdata! If you were/are in my shoes, what would/did you do? I'm a worrier - I think I just need someone to tell me that this is nothing to worry about!

[If I got pregnant, it wouldn't be the end of the world. I'm in grad school and do not want to have a baby now, so I would probably get an abortion. But, um... I'd rather not have to cross that bridge. That's a large part of the reason I got the IUD!]
posted by hefeweizen to Health & Fitness (15 answers total) 4 users marked this as a favorite
Statistically speaking, Mirena is as effective as sterilization. (Mathematically, it's actually slightly MORE effective, but not to a statistically significant degree.) Most of the pregnancies that occur with a Mirena are right at the end of the 5-year period; most of the stories you hear about pregnancies occurring with an IUD are older, less effective models. It's basically the most effective form of reversible birth control that exists.

I know two people who have become pregnant after surgical sterilization (including one woman who had 3 pregnancies, 1 after each of 2 vasectomies and one after a tubal ligation) and nobody who has become pregnant with a Mirena, if anecdotes are more up your alley. :-)
posted by KathrynT at 5:38 PM on October 5, 2012 [13 favorites]

I would not worry about it. The IUD is more effective than hormonal birth control, and probably 99 percent of the times I've had sex in my life we have relied on the pill, and it's worked out fine. You have chosen one of the most reliable birth control methods in the world, and while it's obviously totally fine to keep using condoms (especially if you don't like the mess), there's not much real reason for it.
posted by Forktine at 5:40 PM on October 5, 2012

I'm on my second Mirena now. I have had unprotected sex almost exclusively since getting it, and have never gotten pregnant or even suspected I had.

For whatever it is worth to you, this internet stranger gives you her permission to have unprotected sex.
posted by That's Numberwang! at 5:48 PM on October 5, 2012 [2 favorites]

Got mine over a year ago and haven't used condoms since. To me it is worth the risk and we have discussed what would happen if I did get pregnant, so my partner and I are both on the same page. I'm a bit of a worrier sometimes, but this doesn't worry me.
posted by futureisunwritten at 6:02 PM on October 5, 2012

Out of curiosity, does anyone know if Mirena is more effective than condom+pill, or condom+ring? After all, the OP was comfortable with the risk for condom+pill; should she be more or less comfortable with the risk of Mirena alone?
posted by nat at 6:14 PM on October 5, 2012

It looks like the failure rate for condoms + pill in typical use is around 1.5%, while the failure rate of the Mirena is about 0.2%.
posted by KathrynT at 6:25 PM on October 5, 2012 [3 favorites]

Hey, I get it, there is a weird psychological hurdle to going from condom to no condom, even if the no condom method you are using is more effective (and let's be clear -- IUD is much more effective than even condom + pill). You shouldn't think of "people who got pregnant with an IUD" though. Those cases are really "people who got pregnant because their IUD failed in some way". It's like pregnancy after vasectomy. It happens, in vanishingly rare cases, but it is simply not something that is possible in the normal, predictable course of events. You are lucky in that you seem to have considered what you would do in the event of such an unpredictable event, so you've got all your bases covered. Go to town!
posted by Rock Steady at 7:07 PM on October 5, 2012 [3 favorites]

Here's one summary table:, which says it's from the standard contraception reference book for physicians. It cites a 0.2 percent annual failure rate for Mirena (although other sources, such as, cite 0.1 percent). That table says perfect use of male condoms has a 2 percent failure rate and perfect pill use 0.3 percent, suggesting that perfect use of both would result in 0.006 percent failure rate. So perfect use of both pill and condom would be better than just Mirena. However, with typical use, the failure rates are 15 and 8 percent, suggesting a combined failure rate of about 1.2 percent, similar to what KathrynT cited. However, sterilization has a failure rate of 0.5 percent.
posted by Mr.Know-it-some at 7:09 PM on October 5, 2012

Yeah, the way I used to think about it, if I wasn't comfortable enough to risk a 0.2% risk of pregnancy with a Mirena, I probably shouldn't be having sex, because no birth control method is perfect.
posted by treehorn+bunny at 7:36 PM on October 5, 2012 [4 favorites]

When I first got my Mirena, they said the highest "risk" was in the first few weeks -- not because the IUD was ineffective, but that's the time it's going to fall out if that's going to happen. I would keep using condoms for the first month, and if it's still in place (i.e. you can feel the end of the strings), you're gold.

And I freaking love my Mirena and the security I feel with it.
posted by DoubleLune at 8:40 PM on October 5, 2012

I realized a few years ago that even when I use other birth control, I like to use condoms as well. If you want to keep using condoms while you have an IUD, there's absolutely no harm in that. I say you should do whatever allows you to have pleasurable, worry-free sex.
posted by kate blank at 8:54 PM on October 5, 2012 [2 favorites]

I think the scary stories you may be hearing are about the IUDs of the '70's, when they really hadn't gotten the technology right yet, and the failure rate was not in the acceptable range. IUDs had a lot to come back from after the initially well-proven distrust, but the ones made now are incredibly good with a lot of studies. In the hopes that eases your mind some.
posted by Margalo Epps at 9:14 PM on October 5, 2012

Keep in mind that no one goes around telling the story of how they had an IUD for 5 years and didn't get pregnant. All of the anecdata you've been reading is, to put it bluntly, meaningless from a purely rational point of view. That said, you should do whatever makes you feel comfortable and safe.
posted by matildatakesovertheworld at 10:42 PM on October 5, 2012

And, can I just add something about not using condoms?

I have a similar fear and - short of hysterectomy - I would not, not, not go without a condom.

What made this fear go away was to research the worst case scenario: abortion. As abortion is illegal in my country and would involve travel abroad, I researched the full cost of the whole procedure along with follow-up therapy. I then gathered the money needed (BF donated half, but whatever floats your boat) and stashed it away in a bank account all of its own.

Knowing the full price of an abortion - the ultimate, worst case scenario of going without condoms - was available at a moment's notice finally set my mind at ease. I was able only then to trust my IUD 100%

It's not easy socking away the bones of 3k and just leaving it there for something that may (and probably will) never happen. But. I understand your fear and I've been there. This is what's worked for me.
posted by Chorus at 1:22 AM on October 6, 2012 [4 favorites]

Most of the pregnancies that occur with a Mirena are right at the end of the 5-year period

That's interesting, because I know that Mirena is approved for 7 years outside the US, and that it might be approved for 10 years. Do you have any more info on that?

I think the .2 % failure rate for the first year might exclude those whose IUD was expelled (at least, the rates I found for typical use and perfect use were both .2%, and I'm assuming that perfect use would not include the IUD coming out). The five year failure rate is .7%.

Those are slim odds, but the odds of getting pregnant with condom + IUD must be even slimmer.

If my math is right (and I'm certainly not promising that it is):

Chances of getting pregnant in one year with Mirena : 2 in 1,000
Chances of getting pregnant in one year using condoms-only : 18 in 100 (this is the high end of the stats for typical use. Perfect use is 2 in 100)
Chances of getting pregnant in one year with both: .002*.18 = .00036, or 3 in 10,000

Anecdata: I have an IUD (had a Mirena for 5 years, and when it was due to be replaced I switched to Paragard because of issues I was having with ovarian cysts). A friend of mine got pregnant with an IUD (and yes, it was definitely still in), and even though I knew that 8 in 1,000 women get pregnant each year using Paragard, actually knowing someone who did freaked me out enough that we're talking about combining it with a FAM.
posted by amarynth at 12:13 PM on October 6, 2012

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