OBJECTIVES: To evaluate the effectiveness of cervical pessary for preventing spontaneous preterm birth (SPTB) in singleton gestations with a second trimester short cervix. METHODS: Electronic databases were searched from their inception until February 2016. We included randomized clinical trials (RCTs) comparing the use of the cervical pessary with expectant management in singletons pregnancies with transvaginal ultrasound cervical length (TVU CL) ≤25 mm. The primary outcome was incidence of SPTB <34 weeks. The summary measures were reported as relative risk (RR) with 95% confidence interval (CI). RESULTS: Three RCTs (n = 1,420) were included. The mean gestational age (GA) at randomization was approximately 22 weeks. The Arabin pes...