Cervical cerclage: a review of the evidence.

Cervical insufficiency is a difficult and confusing diagnosis. Its diagnostic criteria, etiology, and treatment are all debated. Cervical cerclage has been a common practice in obstetrics since it was first described by Shirodker and then McDonald in the 1950s. Cerclages have been placed because of a patient's obstetrical history, physical examination, ultrasound, or a combination of the above. However, the data supporting cerclage placement is limited. There has never been a prospective, randomized, controlled trial of cerclage versus no cerclage in patients with a classic history of cervical insufficiency (multiple painless second trimester losses occurring at progressively earlier gestational ages). This article attempts to review the relevant studies regarding cerclage placement for the treatment of cervical insufficiency. Based on the current literature, there is evidence supporting cervical cerclage in the following limited circumstances: a history of 3 or more spontaneous preterm births or second trimester losses; a high-risk patient with a singleton pregnancy who has a short cervix in the second trimester. Because the majority of patients with risk factors for preterm birth and second trimester loss (poor obstetric history, short cervix) will still deliver at term or near-term, studies on the effectiveness of cervical cerclage would need many patients to be powered appropriately.