Since the cervical cerclage was introduced to clinical practice 50 years ago, the efficacy of the operation has not been established by evidence-based standards for many indications. Serious flaws in the methods employed to study the safety and efficacy of cerclage have led to confusion and misuse of the operation, although some investigators maintain that current standards make randomized clinical trials of this traditional surgery unethical. At present, five randomized clinical trials have offered significant information about elective cerclages performed for historical indications, and the expected neonatal survival rate with properly selected elective cerclages is around 87%. Transvaginal ultrasound studies have revealed new paradigms regarding normal cervical function in pregnancy and further understanding about the significance and predictive value of cervical changes at gestational ages between 20-37 weeks. Only two randomized clinical trials have been conducted regarding cerclage in women with decreasing cervical length or with cervical funneling. One of these two failed to demonstrate any resulting improvement in neonatal survival, and the other was too small to be conclusive. To date, no randomized clinical trials have been conducted to demonstrate the efficacy or safety of emergency cerclages performed for advanced cervical dilatation. The many retrospective case series regarding emergency cerclage have failed to provide an evidence-based solution to the management of this problem. Before this traditional surgery continues extensive use in clinical practice, it should be assessed rigorously with randomized clinical trials of sufficient statistical power and external validity to establish the appropriate indications for the operation. In addition, a more thorough understanding of cervical function and molecular biology is essential.
