Cervical Insufficiency

Anthony Sciscione, D.O.

Basic Information

Definition

Gradual, painless dilation of the cervix during pregnancy, leading to recurrent inability to maintain pregnancy beyond the second trimester. Cervical dilation occurs in the absence of clinical contractions and/or labor. Diagnosis is clinical.

Synonyms

Incompetent cervix
Shortened cervix
Preterm birth syndrome

Epidemiology & Demographics

Incidence

1 in 1000 among general obstetrical population

Risk Factors

Prior cervical surgery (e.g., cone biopsy, loop electrosurgical excision procedure [LEEP]), in utero diethylstilbestrol (DES) exposure, prior first- or second-trimester abortions, uterine anomalies, multiple gestations, prior spontaneous preterm births not meeting the criteria for cervical insufficiency

Physical Findings & Clinical Presentation

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Painless cervical dilation during the second trimester
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Nonspecific presentation: backache, pelvic pressure, contractions, vaginal spotting, vaginal discharge

Etiology

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Most cases are either idiopathic or iatrogenic as a result of prior cervical surgery. The cause is thought to be a loss of elastic fibers in the cervices of affected women.

Diagnosis

Differential Diagnosis

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Preterm labor
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Shortened cervix

Work-Up

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Prior obstetrical history, particularly with regard to previous preterm deliveries or spontaneous abortions
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Prior history of any gynecological procedures, especially those involving the cervix
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Serial digital cervical exams
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Serial transvaginal ultrasound

Laboratory Tests

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Amniocentesis with analysis for white blood cell count, glucose, Gram stain, and culture: Abnormal results for any of these markers may indicate a subclinical infection, which increases risk for preterm birth. Abnormalities may help in selecting patients who would benefit from emergent cerclage, although this benefit should be weighed against the inherent risks of amniocentesis.

Imaging Studies

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Transvaginal ultrasound: Cervical shortening on ultrasound may be a diagnostic marker for cervical insufficiency.

Treatment

Nonpharmacologic Therapy

Cerclage has long been the mainstay of treatment for cervical insufficiency (Figs. E1 to E3). However, randomized controlled trials (RCTs) comparing the rates of preterm birth in patients receiving cervical cerclage versus those without cerclage have produced conflicting results, with many studies showing little or no improvement in preterm birth rates. A meta-analysis by Berghella et al (2005) showed that the greatest benefit of cerclage was in women with singleton pregnancies who had experienced a previous preterm birth, and cerclage was actually detrimental to women carrying multiple gestations. The most common risk associated with cerclage is cervical laceration during delivery (1%-13%). Bed rest is often used when there is a threat of preterm birth, although its benefit is not proven and it has detrimental effects for the mother, such as venous thromboembolic events; thus it is not recommended.

FIG.E1

Placement of sutures for McDonald cerclage.

A, We use a double-headed Mersilene band with four bites in the cervix, avoiding the vessels. B, The suture is placed high up in the cervix, close to the cervicovaginal junction, approximately at the level of the internal os.

From Gabbe SG: *Obstetrics*, ed 6, Philadelphia, 2012, Saunders.

FIG.E2

Transvaginal sonogram of the cervix after cerclage placement. The internal os is closed, and there is no funneling. Echogenic spots in the cervix correspond to cerclage *(arrows)*.

From Gabbe SG: *Obstetrics*, ed 6, Philadelphia, 2012, Saunders.

FIG.E3

Abdominal cerclage.

Surgical placement of circumferential Mersilene tape around uterine isthmus and median to uterine vessels. Knot is tied anteriorly.

From Gabbe SG: *Obstetrics*, ed 6, Philadelphia, 2012, Saunders.

Acute General Rx

Ultrasound-indicated cerclage should be placed in women with ultrasonographic evidence of cervical shortening (<25mm) before 24 weeks’ gestation and a history of a preterm birth before 34 weeks. Women who present with painless cervical dilation in the second trimester may be candidates for a physical-exam–indicated cerclage (rescue cerclage) after being ruled out for uterine activity and evidence of infection. Data are limited on the efficacy of placing a physical-exam–indicated cerclage. Women should be counseled about the potential risks of rescue cerclage in the setting of unclear benefit. Placement of a cervical pessary is only currently recommended in the setting of research trial protocols.

Chronic Rx

Prophylactic cerclage (history-indicated cerclage) has been shown by several studies and meta-analyses to be most heavily indicated in women with prior history of multiple preterm births. Women with a history of one or more second-trimester deliveries with no symptoms or signs of labor at the time of the delivery may be candidates for a prophylactic cerclage, placed at 13 to 14 weeks’ gestation. Women with this history should also be offered 17-OH progesterone injections between 16 and 36 weeks.

Disposition

Patients with a singleton pregnancy, prior history of preterm birth, and shortened cervix (<25 mm) on transvaginal ultrasound should be counseled regarding amniocentesis and cerclage placement.

Referral

Patients at risk of preterm labor should be referred to maternal-fetal medicine.

Ferri – Cervical Insufficiency