Mirena + birth control pills?

[kinomaniac87.livejournal.com]

I've had a Mirena for almost two years now. I recently developed a few health issues for which my doctor put me on birth control pills (Microgestin Fe 1.5/30). She did this without removing the IUD, for reasons I won't go into here 'cause then I'd be writing y'all a novel.

Anyway, I forgot to ask her what this means for my chances of pregnancy prevention. Will these two things work together or no? I'm freaking out a little because I know that one of the main ways Mirena works is by thinning uterine lining to prevent implantation, and the birth control pills stop that from happening. I know that as long as I follow the directions I shouldn't ovulate while on the pills, but supposing that did happen, then what?

Comments

[knittinggoddess.livejournal.com]

I may be more optimistic than nickelshoe, but I think even she'd say it's hardly been rendered useless. As far as we know, the Mirena has three methods of action:
* creating a cervical plug
* decreasing the likelihood of ovulation
* decreasing the endometrium
* creating (http://www.medic8.com/healthguide/articles/mirenaiud.html) an inflammatory (http://scholar.googleusercontent.com/scholar?q=cache:wYOWVceu3cYJ:scholar.google.com/+mirena+mechanism&hl=en&as_sdt=1,38&as_ylo=1997) response in the uterus. (http://www.springerlink.com/content/th25n4731215260t/) (There are more (http://scholar.google.com/scholar?start=0&q=mirena+mechanism+sperm+survival&hl=en&as_sdt=1,38&as_ylo=1997), but I don't have access to those journals.)

Of these four, estrogen only negatively impacts one, and us VP civilians don't know exactly to what degree. Your Mirena is already seriously one of the most effective birth controls out there: 99.98% effective! A decrease in the efficacy of one prong is not going to substantially affect the efficacy of the whole device.

Think of it this way: Six years into the Mirena, the cervical plug is pretty decreased. Endometriosis patients usually can only use the Mirena for three years before the hormones decrease to the point that it's no longer useful, so I imagine a 6 yo Mirena has significantly less hormones than that. But a 6-7 yo Mirena is still effective, to the tune of 98.9% over those 7 years. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2971715/) That's with so little hormones, the cervical plug is significantly decreased, and periods have mostly returned.

In other words, it doesn't sound like the HBC is really going to impact your efficacy all that much. Talk to your doc, because they're clearly more of an expert than I am. But don't freak out--you're still using very effective birth control.

[knittinggoddess.livejournal.com]

(And by three methods, I mean four. It's just that the ovulation prong really isn't that primary a force.)