Study: The impact of the Mirena IUD on vaginal bacteria – good, bad or indifferent?

A study​1​ set out to determine the impact of the Mirena levonorgestrel-based hormonal intrauterine device (IUD), discovering that the impact was minimal to negligible.

That is, the Mirena IUD did not have any significant impact on vaginal microflora.

The study into the Mirena IUD and vaginal bacteria

This vaginal microbiome study was on Caucasian women who had no recent pregnancies or other hormone use. The researchers took vaginal, cervical and uterine samples at nine intervals from one week prior to and 12 weeks post-IUD insertion.

A total of 406 samples were taken from 11 women, and studied. There were 355 bacterial species detected, with Lactobacillus crispatus being the most prevalent – almost 50 per cent.

L. crispatus readings of vaginal and cervical samples from the same visit were not significantly different (meaning the vagina and cervix had similar numbers at the same time), with readings after the IUD being inserted likely to be more than 50 per cent L. crispatus.

Conclusion of the study

There are no significant clinical changes in the vaginal microbiome after insertion of a levonorgestrel IUD.


  1. 1.
    Jacobson JC, Turok DK, Dermish AI, Nygaard IE, Settles ML. Vaginal microbiome changes with levonorgestrel intrauterine system placement. Contraception. Published online August 2014:130-135. doi:10.1016/j.contraception.2014.04.006

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Jessica Lloyd - Vulvovaginal Specialist Naturopathic Practitioner, BHSc(N)

Jessica is a degree-qualified naturopath (BHSc) specialising in vulvovaginal health and disease, based in Melbourne, Australia.

Jessica is the owner and lead naturopath of My Vagina, and is a member of the:

  • International Society for the Study of Vulvovaginal Disease (ISSVD)
  • International Society for the Study of Women's Sexual Health (ISSWSH)
  • National Vulvodynia Association (NVA) Australia
  • New Zealand Vulvovaginal Society (ANZVS)
  • Australian Traditional Medicine Society (ATMS)