Cervical Insufficiency

Updated: Apr 19, 2021

Author: Errol R Norwitz, MD, PhD, MBA; Chief Editor: Ronald M Ramus, MD

Overview

Practice Essentials

Cervical insufficiency (cervical incompetence) is defined by the American College of Obstetricians and Gynecologists (ACOG) as the inability of the uterine cervix to retain a pregnancy in the second trimester, in the absence of uterine contractions.[1]

Signs and symptoms

The diagnosis of cervical insufficiency is primarily based on a history of a previous midtrimester pregnancy loss, which can present with the following:

Painless cervical dilatation and bulging fetal membranes upon presentation in the second trimester of pregnancy
Preterm premature rupture of membranes (PPROM)
Rapid delivery of a previable infant
Rare or absent uterine contractions

In women without a history of pregnancy loss, the diagnosis of cervical insufficiency is based on a combination of the following:

Clinical presentation
Physical examination
Ultrasonographic findings

Most patients are asymptomatic, but some may present with any the following symptoms:

Pelvic pressure
Cramping
Back pain
Increased vaginal discharge

See Presentation for more detail.

Diagnosis

Although the diagnosis of cervical insufficiency may be based on a history of midtrimester pregnancy loss, the following measures may also be useful:

Ultrasonographic transvaginal measurement of cervical length – Cervical length has a strong inverse correlation with the risk of spontaneous preterm birth, particularly in women with a history of preterm delivery[2, 3]
Fetal fibronectin (fFN) testing – Studies have demonstrated the utility of fFN testing in addition to cervical length assessment, with a significant improvement in the prediction of preterm delivery in women with a positive fFN and a cervical length of less than 30 mm[4, 5]

See Workup for more detail.

Management

According to a 2014 practice bulletin from the ACOG concerning the management of cervical insufficiency, cervical cerclage, in which a stitch is placed at the cervicovaginal junction, may benefit women with a history of cervical insufficiency or painless cervical dilatation in the second trimester on physical examination.[1]

Cervical cerclage is the mainstay of surgical treatment for cervical insufficiency and is reasonable in the following situations[1] :

History of second trimester pregnancy loss with painless cervical dilatation
Prior cerclage placement for cervical insufficiency
History of spontaneous preterm birth (prior to 34 weeks’ gestation) and a short cervical length (ie, < 25 mm) prior to 24 weeks’ gestation
Painless cervical dilatation on physical examination in the second trimester

The ACOG does not recommend cerclage placement for women with a short cervix who do not have a history of preterm delivery, as it has not been shown to be beneficial in this population. Moreover, cerclage is not recommended for twin pregnancies with a short cervix, as this has been associated with an increased risk for preterm birth. Certain lifestyle approaches, such as activity restriction, bed rest, and pelvic rest, have not been shown to be effective and thus, should not be used to treat cervical insufficiency.[1]

Cerclage can be accomplished either transvaginally or transabdominally. The 2 most common transvaginal techniques are as follows:

McDonald cerclage (see the image below)

McDonald cerclage.
Shirodkar cerclage (see the image below)

Shirodkar cerclage.

Preoperative evaluation should include the following[6] :

Fetal ultrasound assessment for viability, gestational age, and any identifiable anomalies
Clinical evaluation to exclude active bleeding, preterm labor, and PPROM
Consideration of amniocentesis to rule out a subclinical intraamniotic infection, particularly in women with cervical dilatation at the time of presentation

Postoperative care should include consideration of the possible complications, including suture displacement, artificial rupture of membranes, and chorioamnionitis.

Although cervical cerclage has long been the focus of treatment, several studies support the use of progesterone supplementation in women at risk for preterm delivery.[7, 8, 9, 10, 11] In addition, the cervical pessary may be a potential alternative noninvasive treatment for cervical insufficiency, although further study is necessary.[12, 13, 14]

See Treatment for more detail.

Background

Cervical insufficiency is defined by the American College of Obstetricians and Gynecologists (ACOG) as the inability of the uterine cervix to retain a pregnancy in the second trimester, in the absence of uterine contractions.[1] It typically presents as acute, painless dilatation of the cervix, which can lead to a midtrimester pregnancy loss. In women with this history, the risk of recurrence in a subsequent pregnancy is less than 30%.[15]

Pathophysiology

The cervix develops from fusion and recanalization of the distal paramesonephric (Müllerian) ducts, which is complete by approximately 20 weeks' gestation.[16] It is composed of both muscle and fibrous connective tissue, yet the fibrous component is responsible for the tensile strength of the cervix.[17] Cervical insufficiency is thought to be related to a structural defect in tensile strength at the cervicoisthmic junction, but other disorders (eg, decidual inflammation, intrauterine infection, hemorrhage, uterine overdistension) may result in premature cervical shortening, ultimately leading to preterm delivery.[18, 19]

Etiology

Cervical insufficiency may occur as a result of a functional defect in the cervix, which can be due to an anatomic abnormality (congenital Müllerian anomalies), in utero exposure to diethylstilbestrol (DES), or collagen disorders (Ehlers-Danlos syndrome).[20, 21, 22, 23] Acquired causes of cervical insufficiency include obstetric trauma (eg, cervical laceration during labor and delivery), mechanical dilation of the cervix during gynecologic procedures, and cervical conization, which may be performed via cold knife, laser, or loop electrosurgical excision procedure (LEEP).[24, 25, 26, 27] A history of pregnancy termination is also associated with an increased risk of preterm birth, particularly for those women with more than one pregnancy termination.[28, 29] However, in many women, the cause of cervical insufficiency is unknown.

Presentation

History

The diagnosis of cervical insufficiency is primarily based on a history of a prior midtrimester pregnancy loss. Patients typically present with painless cervical dilation and bulging fetal membranes in the second trimester, followed by the rapid delivery of a previable infant. Although most patients are asymptomatic, they may present with pelvic pressure, cramping, back pain, or increased vaginal discharge. Uterine contractions are typically rare or absent. In women without a history of pregnancy loss, the diagnosis is based on a combination of clinical presentation, physical examination, and ultrasound findings.

DDx

Diagnostic Considerations

Preterm birth may result from numerous causes, including spontaneous preterm labor, preterm premature rupture of membranes (PPROM), antepartum hemorrhage, multiple gestation, and indicated preterm delivery for maternal or fetal conditions (eg, hypertensive disorders of pregnancy, fetal growth restriction, nonreassuring fetal heart rate testing). Cervical insufficiency is responsible for only 8-9% of all preterm births, compared with 40-45% with spontaneous preterm labor and 25-30% with PPROM.[18, 19] Clinical and laboratory studies suggest that preterm labor and delivery may result from several pathogenic processes, including premature activation of the fetal hypothalamic-pituitary-adrenal axis, intrauterine infection, decidual inflammation, hemorrhage, and pathological uterine distension.

Differential Diagnoses

Workup

Approach Considerations

The diagnosis of cervical insufficiency is either based on a history of midtrimester pregnancy loss or a combination of clinical presentation, physical examination, and sonographic measurement of cervical length.

Ultrasonography

Sonographic measurement of cervical length, ideally via transvaginal ultrasonography, is useful in the evaluation of these patients. A short cervical length, which is typically defined as less than 25 mm, has been consistently associated with an increased risk for preterm birth, regardless of other risk factors.[2, 3] Cervical effacement appears to begin at the internal os and proceed caudally, with the appearance of a funnel-shaped opening at the internal os ("funneling"), which results in progressive shortening of the cervical canal.[30] However, the presence of funneling does not add appreciably to prediction of the risk for preterm delivery with a short cervical length.[31]

In asymptomatic women with a prior preterm birth, serial transvaginal cervical length screening is typically performed starting at 16 weeks’ gestation and is repeated every 2 weeks until 26-28 weeks’ gestation. For women without a history of preterm delivery, the American College of Obstetricians and Gynecologists (ACOG) recommends transabdominal cervical length assessment at the time of the fetal anatomical survey (between 18 and 22 weeks’ gestation), followed by transvaginal measurement if a short cervical length is suspected.[32] Although a 2013 Cochrane review did not find sufficient evidence to recommend routine cervical length screening for all pregnant women, the ACOG acknowledges that this screening strategy may be considered.[32, 33]

Symptomatic women who present with threatened preterm labor may be evaluated with cervical length measurement in an attempt to predict the likelihood of preterm birth. Even in the presence of uterine contractions, preterm birth is unlikely to occur with a cervical length of greater than 30 mm.[34, 35] Conversely, a cervical length of less than 15 mm in symptomatic women has been shown to predict approximately 60% of the women who will ultimately deliver within 7 days of presentation.[36] When considering women with an intermediate cervical length (between 15 and 30 mm), combining cervical length assessment with fetal fibronectin testing may be particularly useful.[4, 5]

Fetal Fibronectin Testing

Fetal fibronectin (fFN) is a large fetal glycoprotein that promotes cellular adhesion at uterine-placental and decidual-fetal membrane interfaces and is released into cervicovaginal secretions when this extracellular matrix is disrupted, leading to its use as a predictor of preterm delivery.[37] Its use is limited to women with a gestational age between 22 and 34 weeks, as long as fetal membranes are intact and cervical dilatation is less than 3 cm. Sample collection is performed by placing a swab in the posterior vaginal fornix, which should be performed prior to digital or ultrasound examination of the cervix.[38] Several studies have demonstrated the utility of fFN testing, in addition to cervical length assessment, with a significant improvement in the prediction of preterm delivery in women with a positive fFN and a cervical length less than 30 mm.[4, 5]

Treatment

Cervical Cerclage

Surgical treatment of cervical insufficiency has long consisted of cervical cerclage, which is the placement of a stitch in an attempt to improve the tensile strength of the cervix. A cerclage can be placed from a transvaginal or transabdominal approach, with the primary objective of reinforcing the cervix at the level of the internal os and, thus, increasing the functional length of the cervix. Of the most commonly performed transvaginal techniques, the McDonald cerclage is a purse-string suture that passes through the cervical stroma, whereas the Shirodkar cerclage requires dissection of the bladder anteriorly and the rectum posteriorly in order to place the stitch at the level of the internal os. Transabdominal cerclage is typically reserved for patients with anatomic limitations (eg, after trachelectomy) or those with a history of failure of a transvaginal cerclage.[1]

See the images below.

McDonald cerclage.

Shirodkar cerclage.

Transabdominal cerclage.

According to a 2014 practice bulletin from the American College of Obstetricians and Gynecologists (ACOG),[1] possible indications for cervical cerclage in women with singleton gestations include the following[39, 40, 41] :

History of second trimester pregnancy loss with painless cervical dilatation or prior cerclage placement for cervical insufficiency ("history-indicated cerclage")
Painless cervical dilatation in the second trimester ("emergency" or "rescue cerclage")
History of spontaneous preterm birth (prior to 34 weeks’ gestation) and a short cervical length (eg, < 25 mm) prior to 24 weeks’ gestation ("ultrasound-indicated cerclage")

Conversely, cerclage placement has not been shown to be beneficial in women with a short cervix who do not have a history of preterm delivery.[42, 43]

In women with multiple gestations and a short cervix, cerclage placement is not recommended, as this has actually been associated with an increased risk for preterm delivery.[43]

Preoperative evaluation prior to cerclage placement should include ultrasound assessment to ensure fetal viability, confirm gestational age, and rule out any clinically significant fetal anatomical abnormalities. Clinical evaluation for the presence of active bleeding, preterm labor, and preterm premature rupture of membranes (PPROM) should also be performed, as these are contraindications to cerclage placement. In women with evidence of cervical dilatation on physical examination, preoperative amniocentesis may be considered to rule out a subclinical intraamniotic infection, as the rate of infection may be as high as 30% in these cases.[6] Postoperative care should include consideration of the possible complications, including suture displacement, artificial rupture of membranes, and chorioamnionitis.

A review and meta-analysis by Ehsanipoor et al found that physical examination-indicated cerclage significantly increases neonatal survival and extends pregnancy by an average of 33.98 days compared with expectant management.[44, 45]

In a randomized controlled trial, Roman et al found that physical examination-indicated cerclage reduced perinatal mortality by 78% and decreased the incidence of early preterm birth by 50% among women with twin pregnancies and asymptomatic cervical dilation.[46]

Progesterone Supplementation

In a 2012 practice bulletin, the American College of Obstetricians and Gynecologists (ACOG) recommends that women with a prior spontaneous preterm birth should be offered progesterone supplementation (ie, weekly 17-alpha-hydroxyprogesterone caproate), starting at 16-24 weeks’ gestation and continuing up to 36 weeks’ gestation, in order to reduce the risk of recurrent preterm birth.[7, 32] Of note, cervical cerclage has not been shown to offer additional benefit for the prevention of recurrent preterm delivery in these women.[47]

In women without a history of preterm birth, vaginal progesterone has been shown to benefit women with a short cervix, which is defined as less than 20 mm in this population, resulting in a significant reduction in spontaneous preterm delivery.[10, 11] On the other hand, it is unclear whether vaginal progesterone is of benefit to women with a history of preterm delivery, as studies have demonstrated conflicting results.[8, 9] Of note, progesterone supplementation has not been shown to benefit women with multiple gestations.[32]

Cervical Pessary

The cervical pessary has been studied as a potential noninvasive treatment for cervical insufficiency in small series of patients for the past 50 years, but there are limited data from randomized controlled trials. A cervical pessary is thought to alter the axis of the cervical canal and displace the weight of pregnant uterus away from the cervix.[12, 13] One multicenter trial of singleton pregnancies in Spain showed a significant reduction in the preterm delivery rate (ie, < 34 weeks’ gestation) in the pessary group (6%), compared with 27% in the expectant management group (odds ration, 0.18; 95% confidence interval, 0.08-0.37).[14] Further study regarding its use is necessary, but the cervical pessary may become an alternative treatment for cervical insufficiency.

A multicenter, randomized controlled trial by Nicolaides et al found that cervical pessary does not reduce the rate of spontaneous early preterm birth in women and girls with a shortened cervix compared with expectant management. The study’s results found no significant difference between the pessary group (465 participants) and the control group (467 participants) in the rate of spontaneous delivery before 34 weeks and no significant differences in the rates of perinatal death, adverse neonatal outcome, or neonatal special care.[48, 49]

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