Is Transperineal Ultrasonography of Cervical Length in Pregnant Women as Accurate as Endovaginal Ultrasonography? A Prospective, Blinded Comparison of Level of Agreement of Two Techniques

Objectives : To assess the accuracy of transperineal compared to endovaginal sonographic measurement of cervix length, and to assess the feasibility of an obstetrical resident attaining competence in transperineal sonographic measurement of cervix length. Methods : After attaining appropriate concordance in measurement between the three participating investigators (one obstetrical resident and two experienced sonographers), a prospective, blinded study was performed. Paired endovaginal and transperineal cervix length measurements were performed on 123 consenting pregnant women. Results : Concordance between the three investigators was easily established, demonstrating competence in transperineal cervix length measurement by the obstetrical resident. Although there was 85 percent correlation between endovaginal and transperineal cervix length measurements, the predetermined acceptante difference between the two measurements (1-5 mm) was not obtained, demonstrating that transperineal cervical length measurements are not as accurate as endovaginal measurements. ln addition, 15 percent of transperineal assessments were of insufficient quality for interpretations. Conclusions : Transperineal measurements are more difficult to perform well, the quality of the measurements are more often unacceptable, and they may not be as accurate or reliable as endovaginal measurements. It is a realistic objective for obstetrical residents to become competent in sonographic cervix length measurement, suggesting that it could be feasible for residents to perform endovaginal cervix length measurements in a labour and delivery setting for the assessment of women with symptoms of threatened preterm labour.