This chapter reviews the problem of cervical change and cervical insufficiency as related to preterm delivery. Recommendations for surveillance and best practice are made, and the principal surgical procedures for cervical reinforcement (cerclage) are discussed and critiqued. Endovaginal sonography is the best method for the evaluation of women at risk for preterm delivery or cervical insufficiency during pregnancy. Late and uncommon complications of cerclage include fistula formation and, rarely, cervical stenosis. Cicatrix formation can result in cervical dystocia in labor or eventuate in deep cervical lacerations at delivery, which can extend into the broad ligament. Cervical cerclages are best classified based on their timing and the anatomic approach taken for the repair. In terms of timing, these procedures are considered as elective, urgent, or emergent. The current approach to the placement of cerclage is most often transvaginal, and most procedures are performed during pregnancy.