Cervical Incompetence and Cerclage - 1 - An Introduction
Cervical incompetence, or cervical insufficiency, relates to premature, progressive cervical change that subsequently results in preterm delivery and/or pregnancy loss. Most purists will also add the admonition that such change must occur in the absence of uterine activity (i.e., painless cervical dilation and effacement) – a point that was emphasized in my own training and with which I now take major issue. The problems with the study of cervical incompetence are that, like preterm labor, the underlying causes and pathology can be multifactorial, the diagnostic criteria are not consistent, and treatment regimens, including the value and timing of cervical cerclage, are varied and difficult to subject to critical, randomized research because of the vastly different experiences and skill sets of physicians and the sensitive issues related to what is in the balance, specifically, the life of the baby, under circumstances when patient and provider have their backs against the wall and the pervasive attitude is often: “Well, what have we got to lose by trying?” “If we don’t do something, the baby will be lost anyway or delivered so early that he/she is at great risk for mortality or life-long morbidity secondary to prematurity.”
In recent years, the debates on all fronts have come to the fore. The primary reason for this is that prior to the widespread application of ultrasound to the evaluation of the cervix in midtrimester, the diagnosis of cervical incompetence was usually a retrospective one – made only after the preterm delivery and/or loss of one or more babies under circumstances that met the “definition” of cervical incompetence. And, believe me, when the purists got involved and the strict criteria were applied, the debate was often quite heated – “She had some contractions with that pregnancy, so it must have been preterm labor and not cervical incompetence.” “She came in with a fever, so it must have been chorioamnionitis (infection of the membranes) and could not have been cervical incompetence.” “She delivered her last baby at 35 weeks, so how could she have an incompetent cervix.” Anyway, you get the picture. The problem with all these sorts of comments is that they tend to ignore the possibility of “What came first, the chicken or the egg!”
However, now we have a lot of experience with evaluation of the cervix by ultrasound, and some of us have a very low threshold for performing the same under circumstances wherein the patient may be ‘at risk’ for cervical incompetence or when there appears to be premature cervical changes picked up as an incidental finding at the time of a routine ultrasound done at 18-20 weeks for the assessment of fetal anatomy. And, as a result, and as I will detail in subsequent posts, we are now in the position of more often detecting what may be either significant (advanced) premature cervical changes that permit late (“rescue”), but timely, intervention with even a first pregnancy as well as more subtle changes that may or may not indicate the patient is truly at risk for preterm delivery or pregnancy loss. It is the latter group that currently should be approachable by randomized research to clarify the most sensible approach to therapy, but even that is proving more difficult with time.
In this series, I will have several goals: We will provide a basic understanding of cervical structure and illustrate the differences between the cervix and the uterus; we will briefly discuss the biochemical changes that occur in the cervix coincident with cervical change and the factors that might contribute to those events prematurely; we will point out risk factors for cervical incompetence; we will discuss assessment of the cervix by ultrasound; and we will discuss treatment options under various conditions, including my own approach to cerclage – focusing on that approach under pregnancy “rescue” conditions…so, stay tuned!