Cervical modifications after pessary placement in singleton pregnancies with maternal short cervical length: 2D and 3D ultrasound evaluation

Abstract

Introduction The use of a pessary proved to prevent preterm birth in asymptomatic women with mid‐trimester short cervical length (CL); however, the precise mechanisms by which the pessary confers its benefit remain unclear. The aim of this study was to evaluate multiple cervical characteristics assessed by 2‐dimensional and 3‐dimensional ultrasound before and after placement of a cervical pessary to ascertain its mechanism of action. Material and methods In this prospective cohort study, we assessed the cervical characteristics in singleton pregnancies with maternal short CL and compared them with matched reference women with normal CL. The variables evaluated were: CL, uterocervical angles, cervical consistency indices (cervical consistency index and CL consistency index), cervical volume and vascular indices. All variables were re‐assessed immediately after pessary placement and 4‐6 weeks later in all participants. Mann‐Whitney U test was used to assess differences between groups and paired samples t test for comparisons in two different examinations in the same women. The aim of this study was to evaluate multiple cervical ultrasound variables before and after the placement of a cervical pessary and compare the evolution of these variables with a reference group with normal CL to better understand the device's mechanism of action. Results Thirty‐three women with short CL and 24 reference women with normal CL were enrolled. At the time of enrollment, gestational age and maternal baseline characteristics did not differ between groups. Immediately after pessary placement, CL increased, uterocervical angles were narrower and cervical consistency increased significantly. When the magnitude of change in cervical variables was compared over time between the reference group and the study group, median CL had increased in the study group (1.47 mm) but it had shortened in the reference group (−2.56 mm). These inverse trends were statistically significant (P = 0.006). Conclusions Cervical pessary reduces both uterocervical angles and corrects cervical angulation by pushing the cervix up toward the uterus. Maintaining the cervix aligned to the uterine axis leads to reduced cervical tissue stretch, so avoiding further cervical shortening. All these changes were present after pessary placement; however, the clinical implications of these findings remain unknown.

Cervical Pessary Plus Progesterone for Twin Pregnancy with Short Cervix Compared to Unselected and Non-Treated Twin Pregnancy: A Historical Equivalence Cohort Study (EPM Twin Pessary Study)

“…It was only because of the ultrasound that we were able to recognize patients with the pessary in a bad position; after the diagnosis, the device was repositioned in all of those cases. 33,34 Our data also suggest that it was the relocation of the pessary in a bad position that was responsible for the better performance in individual rates of PB (red line) during the study, as demonstrated by the learning curve, even despite the reduction in cervical length (green line) (►Fig. 1).…”

Risk factors of early spontaneous preterm birth despite carrying a cervical pessary in singleton pregnancies with a short cervix: Development of a risk prediction model

“…The pessary modifies uterocervical angulation and increases CL and cervical consistency. [10] In some studies, the pessary has been a valuable intervention for preventing preterm birth in high-risk populations. [11] , [12] , [13] , [14] However, this evidence has not been proven in other studies due to [15] , [16] , [17] , [18] heterogeneity in the inclusion criteria, such as gestational weeks at diagnosis.…”

Prevention of Preterm Birth by Cervical Pessary Combined with Vaginal Progesterone: a Systematic Review and Meta-analysis with Trial Sequential Analysis

“…Progesterone acts the anti-inflammatory roles and anti-cervical ripening by activation of progesterone receptor [ 43 ]. Although the exact mechanisms to explain the contribution of the cervical pessary to prolong pregnancy remain unclear, it may be associated with the following reasons: (1) mechanically changing the utero-cervical angle (defined as the distance between the anterior uterine wall and the axis of the cervical canal) to make it more acute [ 19 , 44 , 45 ] and then preventing direct pressure on the internal cervical os and cervix itself [ 46 ]; (2) preventing further opening of the internal os due to dissociation of amnion and chorion, particularly when the pregnant woman was in the upright position [ 47 ]; (3) protecting the cervical mucus plug through supporting the attachment of the remaining cervical tissue [ 46 ]; and (4) supporting the immunological barrier between the chorioamnion-extraovular space and the vaginal microbiological flora [ 48 ].…”