From concept to practice: the recent history of preterm delivery prevention. Part I: cervical competence.

The prevention of preterm delivery (PTD) is a major desiderate in contemporary obstetrics and a societal necessity. The means to achieve this goal remain elusive, and the research efforts have been punctuated by several ineffective intervention proposals. More recently, new areas of proposed preventive strategy have arisen, focusing on cervical competence, subclinical infection, and hormonal effects. This review, based on a comprehensive and unbiased review of the available literature, will address the rationale and current status of these new concepts of significant clinical interest. We will describe the microcosm of thought and research dedicated to the prevention of PTD during the last 10 years, and the arduous efforts to establish a linkage between predictive observations and therapeutic hypotheses. In its first part, the review will discuss the recently emerging view that regardless of the preterm labor etiology, a common pathway is eventually reached, reflected in cervical changes. The new concept of functional cervical insufficiency is addressed from the perspective of cervical assessment by ultrasound. Although the existing research has not accurately quantified yet the usefulness of ultrasound cervical examination, the technique has become commonplace. Several recent studies have demonstrated a continuum of risk between shorter cervix on ultrasound and higher rate of PTD, leading to the hypothetical argument that women with short cervix on ultrasound might benefit from cervical cerclage. Observational and randomized clinical trials of cerclage as a modality of pregnancy prolongation have provided conflicting results. The relative paucity of data and the conflicting nature of the available evidence dictate caution whenever decisions for cervical monitoring or intervention are made.