Ultrasound Evaluation Versus Direct Measurement of Uterine Cavity Length: A Prospective Study

Abstract

Levonorgestrel intrauterine devices (IUDs) have been successfully used in the adolescent population for menstrual suppression, dysmenorrhea, & contraception.1 Historically, there has been concern regarding the adequacy of the underdeveloped uterine cavity for an IUD.2, 3 Currently, there is no standardized non-invasive way to accurately assess intrauterine cavity length. This study aims to assess the correlation between uterine cavity length on transabdominal pelvic ultrasound (TAUS) to the directly measured uterine cavity length. A prospective cohort study was performed at a single tertiary pediatric gynecology clinic. Patients seen between 1/1/2019-9/29/2021 were eligible if they were planning on an IUD and needed an TAUS. Three additional sonographic curvilinear measurements of the total intrauterine length were collected at the time of the TAUS and interpreted by a single pediatric radiologist. These measurements were then averaged and compared to the directly measured uterine length using a rigid sound at the time of IUD insertion. Past medical history and follow-up information was collected and stored in REDCap for secondary analysis. Institutional IRB approval was obtained prior to recruitment. 47 subjects were recruited, and 38 subjects were analyzed. Patients were on average 16 years old (range 12-21) with a BMI of 25.A two-tailed paired t-test was used to test the hypothesis that there is no difference of the sound length from the average intrauterine TAUS length. There was no statistically significant difference of the sound length from the average TAUS length (p=0.11) and there was a moderate Pearson correlation coefficient (r>0.50, p<0.05). The TAUS uterine cavity length was 0.27cm longer than the uterine sound length. Common indications for IUD insertion included heavy menstrual bleeding (57.9%), dysmenorrhea (47.4%), and menstrual suppression (39.5%). No patients experienced IUD expulsion and there was a 94% satisfaction rate. This study shows that there is no statistically significant difference in uterine sound length from the average TAUS endometrial length. While ultrasound cannot be used as a single qualifying measurement for IUD candidacy, there is moderate correlation of the average measured lengths and the uterine sound length. There is overall high satisfaction with IUD use and low rates of expulsion in this study.