Cervical Incompetence

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Chapter 202 Cervical Incompetence

INTRODUCTION

Description: Cervical incompetence is characterized by asymptomatic dilation of the internal os during pregnancy. This generally leads to dilation of the entire cervical canal during the second trimester with subsequent risk of rupture of the membranes, expulsion of the fetus, or both.

Prevalence: One of 54 to 1 of 1842 pregnancies (as a result of uncertain diagnostic criteria); appears to be declining.

Predominant Age: Reproductive.

Genetics: No genetic pattern.

ETIOLOGY AND PATHOGENESIS

Causes: Iatrogenic (most common); damage from cervical dilation at the time of dilation and curettage (D&C) or other manipulation, damage caused by surgery (conization). Congenital tissue defect, uterine anomalies (uterus didelphys), obstetric lacerations, in utero exposure to diethylstilbestrol (DES).

Risk Factors: In utero exposure to diethylstilbestrol, uterine anomalies.

CLINICAL CHARACTERISTICS

Signs and Symptoms

• History of second-trimester pregnancy loss (generally three or more) accompanied by spontaneous rupture of the membranes without labor or rapid, painless, preterm labor.

• Prolapse and ballooning of the fetal membranes into the vagina without labor.

DIAGNOSTIC APPROACH

Differential Diagnosis

• Uterine anomalies

• Chorioamnionitis

• Chromosomal anomaly (balanced translocation)

Associated Conditions: Premature rupture of the membranes, premature (preterm) delivery, and recurrent second trimester pregnancy loss.

Workup and Evaluation

Laboratory: No evaluation indicated beyond that for routine prenatal care.

Imaging: Ultrasonography before cervical cerclage to ensure normal fetal development. Although cervical length can be measured by ultrasonography, routine use of this has not proved to be an effective screening tool except in the face of a high-risk history. (Normal cervical length is approximately 4.1 cm (±1.02 cm) between 14 and 28 weeks and gradually decreases in length to 40 weeks, when it averages between 2.5 and 3.2 cm.) Signs of cervical funneling and cervical shortening are associated with an increased risk of preterm delivery, but management in the absence of other risk factors is unclear.

Special Tests: None indicated. (Frequent vaginal examinations beginning around the time of previous cervical change or the second trimester, whichever is earlier.) Attempts to define or identify cervical incompetence by hysterosonography, pull-through techniques with inflated catheter balloons, measurement of cervical resistance to cervical dilators, magnetic resonance imaging, and others have not gained clinical acceptance.

Diagnostic Procedures: History.

Pathologic Findings

Painless dilation of the cervix.

MANAGEMENT AND THERAPY

Nonpharmacologic

General Measures: Evaluation, frequent prenatal visits with monitoring for cervical change.

Specific Measures: Cervical cerclage (placement of a concentric nonabsorbable suture at the level of the inner cervical os) is performed between 10 and 14 weeks of gestation. When the suture is placed vaginally, it is generally removed at 38 weeks of gestation. If labor occurs before this point, the suture must be removed immediately. Cervical cerclage is occasionally performed transabdominally. These sutures are intended to remain permanently and preclude vaginal delivery. The use of lever pessaries (such as the Smith-Hodge) has been reported to give outcomes similar to that obtained by cerclage, but this modality is infrequently used. Bleeding, uterine contractions, obvious infection, or rupture of the membranes are contraindications to cerclage. Because of scarring after cerclage, about 15% of patients require cesarean delivery.

Diet: No specific dietary changes indicated.

Activity: Restriction of activity is often suggested, but evidence that this alters the outcome of pregnancy is lacking. After 24 weeks of pregnancy, bed rest may be the only therapy available because cerclage may bring on labor.

Patient Education: American College of Obstetricians and Gynecologists Patient Education Pamphlet AP100 (Repeated Miscarriage), AP110 (Loop Electrosurgical Excision Procedure).

Drug(s) of Choice

None. (Prophylactic antibiotics and beta mimetics have not been shown to be effective.)

FOLLOW-UP

Patient Monitoring: Frequent prenatal visits with monitoring for cervical change in patients thought to be at high risk. If a cerclage is placed, planned removal of cerclage at 38 weeks of gestation is advisable.

Prevention/Avoidance: Care to avoid overdilation of the cervix when surgical manipulation is required.

Possible Complications: Continued fetal loss, chorioamnionitis, cervical avulsion, or uterine rupture if labor occurs and the cerclage is not removed.

Expected Outcome: With correct diagnosis and cervical cerclage, fetal survival increases from 20% to 80%.

MISCELLANEOUS

ICD-9-CM Code: 622.5.

Berghella V, Odibo AO, Tolosa JE. Cerclage for prevention of preterm birth in women with a short cervix found on transvaginal ultrasound examination: a randomized trial. Am J Obstet Gynecol. 2004;191:1311.

Lazar P, Gueguen S, Dreyfus J, et al. Multicentred controlled trial of cervical cerclage in women at moderate risk of preterm delivery. Br J Obstet Gynaecol. 1984;91:731.

Belej-Rak T, Okun N, Windrim R, et al. Effectiveness of cervical cerclage for a sonographically shortened cervix: a systematic review and meta-analysis. Am J Obstet Gynecol. 2003;189:1679.

Drakeley AJ, Roberts D, Alfirevic Z. Cervical cerclage for prevention of preterm delivery: meta-analysis of randomized trials. Obstet Gynecol. 2003;102:621.

Harger JH. Cerclage and cervical insufficiency: an evidence-based analysis. Obstet Gynecol. 2002;100:1313.

Kushnir O, Vigil DA, Izquierdo L, et al. Vaginal ultrasonographic assessment of cervical length changes during normal pregnancy. Am J Obstet Gynecol. 1990;162:991.

American College of Obstetricians and Gynecologists. Cervical insufficiency. ACOG Practice Bulletin 48. Obstet Gynecol. 2003;102:1091.

American College of Obstetricians and Gynecologists. Ultrasonography in pregnancy. ACOG Practice Bulletin 58. Obstet Gynecol. 2004;104:1449.

Cunningham FG, Gant NF, Leveno KJ, et al, editors Williams obstetrics 21st ed. 2001 McGraw-Hill New York 862

McDonald IA. Incompetence of the cervix. Aust N Z J Obstet Gynaecol. 1978;18:34.

Romero R, Espinoza J, Erez O, Hassan S. The role of cervical cerclage in obstetric practice: can the patient who could benefit from this procedure be identified? Am J Obstet Gynecol. 2006;194:1.

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