By Dr. Lisa Nakajima (biography, no disclosures)
What I did before
Intrauterine contraceptive device (IUD) use for contraception and management of heavy uterine bleeding is widespread, with approximately 14% of women aged 15-49 years of age using them worldwide1. It provides highly effective long-term birth control that is easily reversible. One of the risks of IUD insertion includes perforation of the uterus, which has an estimated incidence of 0.4-1.6 perforations per 1000 insertions. Risk factors for perforation include insertion performed by a less experienced clinician, patient lactation, less that 6 months post-partum, lower parity and a higher number of previous abortions1. Additionally, there is increased risk of uterine perforation with the use of a rigid sound or inserter, though I have always used a metal sound for this procedure, as this is how I was taught and what was demonstrated in medical school and residency.
What changed my practice
This past summer, working with a rural family physician who inserts many IUDs, I observed the use of a plastic endometrial aspirator as a uterine sound instead of a rigid metal sound. This was to decrease the risk of perforation. Looking at the literature, there have not been any randomised control trials on the use of sounds for insertion of IUDs. There are no studies looking at the rates of perforation between IUD insertions with or without sounds, let alone with metal versus plastic sounds, though it logically makes sense. There are investigators that question even the use of any sound and its actual benefit in an IUD insertion2.
One of the early IUDs includes a device called the Birnberg Bow, which had a rigid inserter, and a high uterine perforation rate of 1 in 2001. In the 1980s, in vitro studies showed that the force required to perforate a uterus with a metal sound was about 20 N and it would easily pass through the cornual, fundal, and lateral musculature3. Furthermore, the amount of force required to insert an IUD varied from 0.1 to 8 N. IUDs with flexible inserter tubes tended to bow if there was excessive cervical resistance and they were unable to perforate the uterus. These inserters would allow up to 10 N of force before bowing. There are no published studies on the newer and more commonly used devices, like the Mirena and Kyleena, looking at the amount of force required for their insertion.
What do I do now
Although uterine perforation is relatively uncommon and often does not cause long-term harm, it does increase the risk of unplanned pregnancy and often requires surgery to remove it. Consensus opinion states that perforation most commonly occurs at the time of insertion. In addition to perforation, metal sounds can also create false tracks. Therefore, I have chosen to use endometrial aspirators that are commonly used for endometrial biopsy sampling as a sound for IUD insertions, instead of the traditional metal sounds. The cost of an endometrial aspirator is about $4.95, which can be compared to the cost of sterilizing a metal sound in one’s clinic, and they are available in diameters that are similar to the IUDs themselves, often 3 or 4 mm. The Mirena IUD inserter has an outer diameter of 4.4 mm, while the smaller Kyleena IUD inserter is only 3.8 mm4&5. There is no data on the rates of endometrial perforation using an endometrial aspirator.
As mentioned previously, there is little literature on the actual benefit of sounding the uterus prior to this procedure. However, an IUD device can be quite costly financially to many patients, upwards of $400, and thus when practicing patient-centred medicine, this must be considered. When performing this procedure, I sound the uterus with an endometrial aspirator prior to opening the IUD. This way, if I am unable to pass the sound through the cervix, or if the uterus sounds to less than 6 cm, the device is not wasted. This allows me time to troubleshoot. At this point, I may consider re-attempting the procedure during menstruation, when the os is slightly wider. I may have her return after misoprostol 200 mg per vagina the night before. Or I may refer her to a more experienced physician.
- Rowlands S, Oloto E, Horwell DH. Intrauterine devices and risk of uterine perforation: current perspectives. Open Access J Contracept. 2016;7:19–32. DOI: 10.2147/OAJC.S85546. (View)
- Goldstuck ND. A minimalist technique for insertion of intrauterine devices. Healthc Low Resour Settings. 2015;3(1):5067. DOI: 10.4081/hls.2015.5067. (View)
- Goldstuck ND. Insertion forces with intrauterine devices: implications for uterine perforation. Eur J Obstet Gynecol Reprod Biol. 1987;25(4):315–323. DOI: 10.1016/0028-2243(87)90142-0. (Request with CPSBC or view with UBC)
- Bayer Healthcare Pharmaceuticals Inc. Mirena Full Prescribing Information. Revised June 2017. Accessed November 8, 2018. (View)
- Bayer Inc. Kyleena Product Monograph. Published 2018. Accessed November 8, 2018. (View)