Stabilization of cervical stiffness associated with cervical pessary placement in women at risk for preterm birth

Purpose: Shortening of the cervix is a predictor of spontaneous preterm birth (PTB). It is assumed that a cervical pessary reduces mechanical stress on the internal os and consequently decreases the risk of premature delivery. The primary aim of this study was to compare longitudinal changes in cervical stiffness between women with cervical shortening (a cervical length ≤ 25 mm according to the ISUOG guidelines) treated with a cervical pessary and healthy controls. Methods: A total of 89 pregnant participants were analysed in this prospective observational study. Among them, 30 received a cervical pessary because of cervical shortening below 25 mm. The remaining 59 women served as the control group. Cervical stiffness was measured with the Pregnolia® system at two time points: between 18 + 0 and 24 + 6 weeks of gestation (first appointment) and again 4 weeks later. In the pessary cohort, the baseline measurement was obtained prior to pessary insertion. Results: At four weeks, women in the control group demonstrated a decrease in the median Cervical Stiffness Index (CSI) value: 60.8 vs. 46.7 mbar (nominal p = 0.03) although this difference did not remain statistically significant after FDR adjustment (p = 0.09). In contrast, median CSI values remained stable in the pessary group (71.2 vs. 73.7 mbar; p = 0.88). Cervical length and uterocervical angle (UCA) did not change within the observation period in either group. Moreover, the median birth weight in the normal cohort and in the Pessary cohort was 3380 g (3175–3570) and 3185 g (3011–3450), respectively (p = 0.062). Conclusion: In women with the cervical shortening treated with the pessary cervical stiffness remained stable, whereas a decline was observed in the control group. These findings support a potential association between cervical pessary treatment and stabilisation of cervical stiffness. Further studies, including untreated women with cervical shortening are needed to confirm these findings and to better understand the underlying biomechanical mechanisms.