Prospective Open-label Multicentre Randomized Controlled Trial. high-risk preterm pregnancy is that there are at least one history of spontaneous preterm birth and/or late abortion before 34+0 weeks, for high-risk pregnant women that meet the inclusion criteria, the early treatment with cerclage pessary at 12-18weeks compare with routine treatment. The patients will be informed of the intended therapeutic effect and possible side effects. If they agree and after obtaining their informed consent, they will be randomized to test group (cerclage pessary group) and control group (Utrogestan group).
Verify the safety and effectiveness of the cerclage pessary in the prevention and treatment of high-risk preterm pregnancy.