Objective  To study and compare the clinical effects of cervical pessary and progesterone for preventing preterm birth in singleton pregnant women with a short cervical length (CL).

Methods  This study was a prospective cohort study. A total of 148 pregnant women with CL≤25 mm, as determined by ultrasound examination performed before 28 weeks of pregnancy, were included in the study. All subjects were admitted to West China Second Hospital, Sichuan University between August 2020 and December 2022. According to their treatment plans, the pregnant women were divided into a cervical pessary group (n=55) and a progesterone group (n=93). Spontaneous preterm birth before 37 weeks of pregnancy was defined as the main outcome index. Preterm birth (abortion) or spontaneous preterm birth (abortion) before 37, 34, 32, 30, and 28 weeks of pregnancy, mean extended gestational age, neonatal morbidity, and neonatal mortality were the secondary outcome indicators. The pregnancy outcomes and the neonatal outcomes of the two groups were compared and statistically analyzed.

Results  There was no statistically significant difference in the incidence of preterm birth (including iatrogenic preterm birth, spontaneous preterm birth, and abortion) before 37, 34, 32, 30, and 28 weeks between the cervical pessary group and the progesterone group. When iatrogenic preterm birth was excluded, the incidence of spontaneous preterm birth before 37 weeks was lower in the cervical pessary group (23.6%) than that in the progesterone group (41.9%), with the difference between the two groups being statistically significant (P=0.024). There was no statistically significant difference in the incidence of spontaneous preterm birth (including miscarriage) before 34, 32, 30, and 28 weeks. There was no statistically significant difference in the incidence of neonatal morbidity, the rate of transfer to the neonatal care unit after birth, and the neonatal mortality rate between the two groups. Multivariate logistic analysis showed that treatment with cervical pessary was a protective factor for spontaneous preterm birth before 37 weeks compared to progesterone therapy.

Conclusion  Using cervical pessary to prevent spontaneous preterm birth in singleton pregnant women with a short cervical length in the second trimester can significantly reduce the incidence of spontaneous preterm birth before 37 weeks.