Mirena, how it works?

iVillage Member
Registered: 07-01-2004
Mirena, how it works?
5
Wed, 10-27-2004 - 2:23pm
I am considering using Mirena as a method of BC. It is very important to me though that whatever I use works as contraception, as opposed to an abortive. From what I can see Mirena works in three manners, thickening of mucous, some prevention of ovulation, and a thinning of the uterus lining. Does any know, or know where I might find, information on the "percentages" of each of these? Or which manner is most frequent, middle, and least frequent?

Any help, info or direction would be appreciated.

iVillage Member
Registered: 12-30-2003
Wed, 10-27-2004 - 5:10pm
Hi kellim45, welcome!

It depends on when you believe life begins. I think the prevailing view in the medical community is that life begins at implantation. Using that definition no hormonal method of contraception is considered an abortifacient.

Have you looked at the prescribing information on the Mirena site http://www.mirena-us.com/ ? It says:

“MIRENA has mainly local progestogenic effects in the uterine cavity. Morphological changes of the endometrium are observed, including stromal pseudodecidualization, glandular atrophy, a leucocytic infiltration and a decrease in glandular and stromal mitoses.

Ovulation is inhibited in some women using MIRENA. In a 1-year study approximately 45% of menstrual cycles were ovulatory and in another study after 4 years 75% of cycles were ovulatory.

The local mechanism by which continuously released levonorgestrel enhances contraceptive effectiveness of the IUS has not been conclusively demonstrated. Studies of MIRENA prototypes have suggested several mechanisms that prevent pregnancy: thickening of cervical mucus preventing passage of sperm into the uterus, inhibition of sperm capacitation or survival, and alteration of the endometrium.”

From this it appears that during the first year ovulation suppression is the primary means but you see after 4 years ovulation suppression drops to 25% so some other mechanism becomes primary. The way the information is provided in the prescribing information suggests that cervical mucus, inhibition of capitation and alteration of the endometrium, are effective in that order but since the local mechanism has “not been conclusively demonstrated” I don’t think the manufacturer knows for sure. You’ll let us know what you decide, right?

Good luck,

      Jill

    

iVillage Member
Registered: 03-27-2003
Wed, 10-27-2004 - 6:28pm
check out

www.mirena.com/

iVillage Member
Registered: 08-11-2004
Wed, 10-27-2004 - 7:31pm
There's a study here that shows that IUDs act the majority of the time to prevent fertilization from ever occuring:

http://www.fhi.org/en/RH/Pubs/Network/v16_2/nt1623.htm

If it's extremely important to you though that the method you use never has any possibility to prevent implantation from occuring, you might want to consider fertility awareness and/or condoms. Those can be very effective and might fit with your concerns better.

iVillage Member
Registered: 07-01-2004
Mon, 11-22-2004 - 11:27am

Thanks for the feedback. I've since had an appt. with my doc, and he had roughly the same opinion and cited a study about the changes in the mucous that inhibit the sperm ever reaching the egg.

Interesting to hear the that the "prevailing" opinion of the medical community about when life begins. I know that when I asked my dr. about it, I said that preventing conception is very important to me. To me that means egg not meeting sperm, I'll be sure to clarify this at the next appt., and make sure that this is still a solution that will work for us.

Again, thanks for taking the time to reply back and interpreting all that medical/pharmocological/science stuff.

iVillage Member
Registered: 12-30-2003
Mon, 11-22-2004 - 2:44pm

I don't believe you said what contraceptive method you are currently using, but if an IUD doesn't meet your needs then you might want to consider using a cervical barrier (a diaphragm or cervical cap) or using Fertility Awareness Method (FAM) or Natural Family Planning (NFP) to avoid pregnancy. Barriers can be very effective if used correctly and consistently and FAM/NFP is extremely effective if all the rules are followed all the time. There is a post in the FAQs with an overview on cervical barriers and a very good book on the menstrual cycle and Fertility Awareness is Taking Charge of Your Fertility by Toni Weschler. For more on the pros and cons of various contraceptive methods and an effectiveness comparison see the Planned Parenthood links: Contraceptive Choices http://www.plannedparenthood.org/bc/cchoices.html and Method Effectiveness http://www.plannedparenthood.org/bc/bcfacts2.html I hope you will let us know what you decide.

Good luck,

      Jill