Cervical Competence: Are There Reasons For Not Using Cerclage?

My sister, who is 22 weeks pregnant, has just been diagnosed with an incompetent cervix after suffering a bout of preterm contractions which they were able to halt with Brethine. Her physician sent her to a high-risk specialist, a long distance away, for a cervical cerclage. The specialist told her that she had thinned from "36" to "23" in one week's time, and opted not to perform the cerclage. Instead, he wants her to make the long drive one a week, every week throughout her pregnancy. Why would a physician opt not to perform a cerclage?


Peg Plumbo CNM

Peg Plumbo has been a certified nurse-midwife (CNM) since 1976. She has assisted at over 1,000 births and currently teaches in the... Read more

How wonderful to have a sister like you. I can certainly understand your concern.

In general, according to Gabbe's Pregnancy, Normal and Problem Pregnancies, when the diagnosis is made before cervical dilatation has occurred and when there is still 10 to 15 millimeters or more of cervical length (which she does have), they recommend admitting the client to the hospital for a day and treatment with indomethacin (a anti-inflammatory drug) and antibiotics. Cerclage sutures would then be placed, followed by observation for two to four days. If dilatation has occurred so that the membranes are visible observation woud increase to seven days.

Generally, however, there is much more to cervical competence than cervical length and there is more to a cervix than just length.

The ultrasound characteristics of reduced cervical competence are a short cervix (less than 20 millimeters) often, but not always, accompanied by "funneling" of the internal os. Funneling is thought of as "effacement in progress," and the process proceeds from the inside out, beginning at the internal opening and moving toward the external cervical opening. The process can be changed with the addition or alleviation of pressure to the top of the uterus or applied above the pubic bone or by the standing position.

If a woman has no history of preterm birth, Gabbe says, "...the appearance of this funneling," whether spontaneous or induced by applying pressure to the top of the uterus or behind the pubic bone, "does not establish a diagnosis of cervical incompetence nor does it require a cerclage." These experts place greater significance on the cervical length.

I guess the bottom line is that this does seem to be a significant amount of cervical thinning, but still not less than 20 millimeters. I'm guessing that the weekly trips are for ultrasound to follow the thinning; if it does reach the point of "too short," a cerclage will be done.

See if they do the test where during ultrasound, pushing on the top of the uterus, causes increased changes. This has been shown to be predictive of preterm birth. Ultrasound is done transvaginally and continues during the pushing procedure.

It does seem unreasonable to expect these long trips with a woman at her level of risk. She should definitely avoid prolonged standing and lifting or any other strenuous activity, including intercourse for a while.

Editor's Note: A study in the September 2003 issue of Obstetrics & Gynecology finds that the use of cervical cerclage is not effective in preventing preterm birth or miscarriage in women at moderate risk of preterm birth or second-trimester pregnancy loss.

Guzman ER. Houlihan C. Vintzileos A. Ivan J. Benito C. Kappy K.
The significance of transvaginal ultrasonographic evaluation of the cervix in women treated with emergency cerclage.
American Journal of Obstetrics & Gynecology. 175(2):471-6, 1996 Aug.
OBJECTIVE: Our purpose was to determine whether perioperative transvaginal ultrasonographic evaluation of the incompetent cervix treated with emergency cerclage is predictive of pregnancy outcome.

STUDY DESIGN: Twenty-nine women who underwent emergency cerclage at 16 to 26 weeks of gestation had transvaginal ultrasonographic evaluation of the cervix within 48 hours before and after surgery and at least three times thereafter until 28 weeks of gestation. The following measurements were obtained: (1) funnel width, (2) funnel length, (3) endocervical canal length, (4) the distance between the internal and external os, (5) upper cervix (length of closed endocervical canal above the cervical cerclage), (6) lower cervix (endocervical canal length below suture), and (7) cervical index (1+ Funnel length/Endocervical canal length). Values are reported as the median in millimeters, and statistical analysis was performed by use of the Mann-Whitney U test, Wilcoxon signed-rank test, Spearman rank correlation, 2 x 2 contingency tables, and multiple regression analysis with significance set at p <0.05.

RESULTS: Cerclage procedures resulted in significant improvement in postoperative median measurements of funnel width (15 vs. 4.0 mm, p <0.0001), funnel length (29 vs. 3 mm, p <0.0001), and endocervical canal length (2 vs. 27 mm, p <0.0001). There was a significant relationship between gestational age at delivery and the following measurements: preoperative funnel width (r = -0.51, p = 0.007), postoperative endocervical canal length (r = 0.39, p = 0.04), length of the lower cervix (r = 0.39, p = 0.038), and the cervical index (r = -0.39, p = 0.038). An upper cervical length <10 mm was a good predictor of delivery before 36 weeks of gestation, sensitivity 85.7 percent (12/14), specificity 66.7 percent (10/15), positive predictive value 70.6 percent (12/17), negative predictive value 83 percent (10/12), and Fisher's exact p = 0.008. Postoperatively all patients had upper cervical lengths <10 mm by 28 weeks of gestation. Preoperative digital assessments of cervical dilatation before surgery did not correlate with gestational age at birth (r = -0.031, p = 0.36).

CONCLUSIONS: In cases of cervical incompetence treated with emergency cerclage, perioperative transvaginal ultrasonographic assessment of the cervix reveals that the procedure results in improved ultrasonographic status of the cervix and that the ultrasonographic cervical findings before and after surgery correlate with pregnancy outcome.

Guzman ER. Houlihan C. Vintzileos A.
Sonography and transfundal pressure in the evaluation of the cervix during pregnancy. [Review] [28 refs]
Obstetrical & Gynecological Survey. 50(5):395-403, 1995 May.
Ultrasonographic evaluation of the cervix in pregnancy has provided some insight into premature delivery and pregnancy wastage. Its use has led to the development of cervical length nomograms in uncomplicated singleton pregnancies and to the realization that varying degrees of cervical incompetence exist. In some instances, the internal os has been observed to dilate and funnel in the early second trimester while in others these changes occur gradually into the third trimester. Transient cervical changes have been linked to premature delivery, and extended ultrasonographic inspection is required for their detection. Although sonography may allow the identification of women who deliver prematurely, it has not demonstrated enough discriminatory power to recommend its routine use for this purpose. Pre- and postoperative inspection of the cervix in elective and emergency cerclage procedures may become influential in outpatient management. A method of functional evaluation of the cervix using transfundal pressure (TFP) has been introduced which may lead to earlier diagnosis of cervical incompetence. The significance of descent of the membranes in response to TFP and sonographic findings consistent with premature cervical changes have not been validated because of surgical intervention performed in response to these findings. Our review concludes that, although sonography of the cervix may be useful in selective cases, more information on the natural history of abnormal cervical sonographic findings and controlled randomized trials are needed before recommendations on surgical intervention can be made. [References: 28]
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