ABSTRACT & COMMENTARY
Predicting Painful IUD Insertion
By Rebecca H. Allen, MD, MPH
Assistant Professor, Department of Obstetrics and Gynecology, Warren Alpert Medical School of Brown University, Women and Infants Hospital, Providence, RI
Dr. Allen is a retained consultant for Bayer.
In this prospective cohort study of 161 nulligravid women, there was no reliable threshold of uterine length or flexion angle measurements that were predictive of painful or difficult insertions. History of severe dysmenorrhea was the only predictor of insertion pain.
Kaislasuo J, et al. Predicting painful or difficult intrauterine device insertion in nulligravid women. Obstet Gynecol 2014;124:
345-353.
This is a prospective cohort study of 161 nulligravid women naïve to intrauterine device (IUD) insertion recruited in Helsinki, Finland, between January 2011 and July 2012. Participants chose the IUD they desired: either the copper IUD or the levonorgestrel (LNG) IUD. Women with contraindications to IUD use were excluded. Women were instructed to take either 800 mg ibuprofen or 1000 mg acetaminophen 1 hour before insertion. Misoprostol was not routinely used. All the IUD insertions were performed by a single experienced physician. Of note, all insertions were performed during menses except for women who had amenorrhea from prior contraceptive use. Before insertion, uterine position was determined from bimanual exam and transvaginal ultrasound was performed to measure the uterine length (length of uterine cavity plus cervical length) and width (cornu to cornu). Flexion angle between the cervix and uterus was also calculated. The length of the uterus as measured by metallic uterine sound was recorded. Insertion pain was evaluated immediately after insertion by the woman and physician, and insertion difficulty was rated by the physician.
The majority of women (68.5%) chose the LNG-IUD, and they were slightly younger (23 years vs 25 years, P = 0.03) and reported more menstrual bleeding (heavy flow 36.4% vs 7.8%, P = 0.001) and pain (severe dysmenorrhea 25.5% vs 3.9%, P = 0.001) than women choosing the copper IUD. The mean uterine sound measurement was 75 ± 7.6 mm and the mean total uterine length by ultrasound was 64.1 ± 8.4 mm for a difference of 11.7 ± 7.9 mm. The mean fundal width was 23.1 ± 3.9 mm. The mean flexion angle was 119.6º (range 61º to 173º). Most insertions (89.4%) were classified as easy. In 15 women, the insertion was difficult; 13 of these women used the LNG-IUD. In 10 of these, cervical dilation was required with metallic Hegar dilators, with six women receiving a paracervical block and three women receiving misoprostol. Only two insertions failed, one because of pain (copper IUD) and one because of a uterine sound measurement of 45 mm (LNG-IUD). In multivariable analysis, insertion difficulty was correlated with smaller total uterine length and smaller flexion angle even when controlling for type of IUD, age, body mass index (BMI) > 30 kg/m2, uterine position, bleeding status at insertion, and other uterine measurements. Nevertheless, there were no threshold measurements that were adequate predictors of insertion difficulty. All women reported pain during insertion — 18 women (11.2%) had mild pain, 49 (30.4%) had moderate pain, 91 (56.5%) had severe pain, and 3 (1.9%) had intolerable pain. In multivariable analysis, the only predictor of pain was a history of severe dysmenorrhea, even when controlling for uterine measurements, type of IUD, bleeding at insertion, uterine position, age, BMI, smoking, dyschezia, dyspareunia, other abdominal pain, and prior cervical procedures.
COMMENTARY
National organizations have endorsed the use of IUDs in adolescents and nulliparous women.1-3 As more nulligravid and nulliparous women are choosing IUDs for contraception, it is important to elucidate factors that may contribute to more painful or difficult insertions. There has been concern that the size of a nulligravid woman’s uterus would be too small to accommodate the copper T380A IUD or the higher dose LNG-IUD, both of which measure 32 mm × 32 mm.4,5 This may lead to more complaints about pain and bleeding leading to removal requests. Additionally, while the inserter for the copper IUD is the smallest, measuring 3.65 mm in diameter, the inserter for the LNG-IUD currently measures 4.75 mm (a 4.4 mm inserter will be released shortly). The newly released, smaller, lower-dose LNG-IUD measures 28 × 30 mm and has a 3.8 mm inserter. The size of the inserter has been correlated to pain and difficulty with insertion in some studies.6
This study attempted to determine whether uterine position or uterine size by ultrasound could predict difficulties with and pain at insertion for nulligravid women. It is one of the first studies attempting to accomplish this in a prospective fashion with the IUDs currently available. A previous study by radiologists reported that the mean uterine cavity width of premenopausal nulliparous women was 27 mm compared to those with one birth (30 mm) and those with more than one birth (31 mm).7 The radiologists concluded that "physicians should consider ultrasonography to measure the uterine cavity before inserting an intrauterine device." However, while this would certainly increase business for radiologists, it would significantly add to the cost and increase barriers to IUD insertion.
Similarly, in the current study, it is interesting to note that most of the women had uterine cavity sizes smaller than the copper IUD and higher-dose LNG-IUD. One-third of women had a cavity length that was smaller and nearly all had a cavity width that was narrower. Despite this, 90% of insertions were assessed as easy. Indeed, although more acute flexion angles were associated with insertion difficulty, there was no threshold ultrasound measurement that was able to reliably predict difficulty or pain with insertion. As this study shows, given an experienced inserter, difficult insertions are likely accounted for by a tight cervix and not uterine size. Most difficult insertions can be solved with cervical dilation and straightening the uterus with a tenaculum to reduce flexion. Therefore, providers planning to insert IUDs in nulligravid and nulliparous women should have the ability to provide cervical dilation as well. I am relieved to know that pre-insertion ultrasounds are not necessary for this population. After insertion, previous studies have shown that the majority of nulliparous women are very satisfied with IUDs and have continuation rates equal to multiparous women.7,8
Finally, the use of the smaller, lower-dose LNG-IUD in this population would not necessarily solve the size issue, as approximately 20% had a shorter cavity measurement and 90% had a narrower cavity measurement. However, the inserter is more narrow than for the higher-dose LNG-IUD, which may facilitate insertions in this population. The fact that history of severe dysmenorrhea predicted pain with insertion is no surprise given that the insertion can irritate the uterus. This may be one variable to ask our nulliparous patients about and, if positive, offer them a paracervical block with insertion.
References
- ACOG Committee Opinion no. 450: Increasing use of contraceptive implants and intrauterine devices to reduce unintended pregnancy. Obstet Gynecol 2009;114:1434-1438.
- Centers for Disease Control and Prevention. U.S. Medical Eligibility Criteria for Contraceptive Use, 2010. MMWR Recomm Rep 2010;59:1-86.
- American College of Obstetricians and Gynecologists. Committee Opinion No. 539. Adolescents and long-acting reversible contraception: Implants and intrauterine devices. Obstet Gynecol 2012;120:983-988.
- Schipp TD, et al. The width of the uterine cavity is narrower in patients with an embedded IUD compared to a normally positioned IUD. J Ultrasound Med 2010;29:1453-1456.
- Benacerraf BR, et al. Width of the normal uterine cavity in premenopausal women and effect of parity. Obstet Gynecol 2010;116(2 Pt 1):305-310.
- Gemzell-Danielsson K, et al. A randomized, phase II study describing the efficacy, bleeding profile, and safety of two low-dose levonorgestrel-releasing intrauterine contraceptive systems and Mirena. Fertil Steril 2012;97:616-622.
- O’neil-Callahan M, et al. Twenty-four-month continuation of reversible contraception. Obstet Gynecol 2013;122:1083-1091.
- Rosenstock JR, et al. Continuation of reversible contraception in teenagers and young women. Obstet Gynecol 2012;120:1298-1305.
