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INTRODUCTION — Classically, the term "cervical insufficiency" was used to describe painless cervical dilation leading to recurrent second-trimester pregnancy losses/births of otherwise normal pregnancies. Structural weakness of cervical tissue was thought to cause or contribute to these adverse outcomes. The term has also been applied to women with one or two such losses/births or at risk for second-trimester pregnancy loss/birth.
Although structural cervical weakness is the source of some second-trimester losses/births, most are caused by other disorders, such as decidual inflammation/infection, hemorrhage, or uterine overdistension. These disorders, which are not typically recurrent, can initiate biochemical changes in the cervix that lead to premature cervical shortening and, often, pregnancy loss. (See "Pathogenesis of spontaneous preterm birth".)
RISK FACTORS — Congenital and acquired cervical abnormalities increase the risk of cervical insufficiency; acquired risk factors are more common. Cervical trauma may occur during labor or delivery (spontaneous, forceps- or vacuum-assisted, cesarean) , rapid mechanical cervical dilation before a gynecologic procedure [2,3], or treatment of cervical intraepithelial neoplasia. Congenital abnormalities include genetic disorders affecting collagen (eg, Ehlers-Danlos syndrome) [4-6], uterine anomalies [7,8], in utero diethylstilbestrol (DES) exposure , and biologic variation.
Past obstetrical history — The past obstetrical history of women with cervical insufficiency is characterized by:
●History of second-trimester pregnancy losses/deliveries, often associated with a short labor
●History of progressively earlier deliveries in successive pregnancies
Symptoms — Women with cervical insufficiency may be asymptomatic or may present with mild symptoms, such as pelvic pressure, premenstrual-like cramping or backache, and/or a change in the volume, color, or consistency of vaginal discharge. Volume may increase; color may change from clear, white, or light yellow to pink, tan, or spotting; and consistency may become thinner. These symptoms may begin between 14 and 20 weeks of gestation and may be present for several days or weeks before diagnosis of cervical insufficiency.
Contractions are absent or mild.
Physical examination — The initial clinical examination may reveal a soft, somewhat effaced cervix, with no or minimal dilation . Provocative maneuvers such as suprapubic or fundal pressure or the Valsalva maneuver may reveal fetal membranes in the endocervical canal or vagina; this is always an abnormal finding. Tocodynamometry shows no or infrequent contractions at irregular intervals.
Late clinical presentation is characterized by advanced dilation and effacement (eg, ≥4 cm dilated and ≥80 percent effaced), spotting, unprovoked grossly prolapsed membranes or ruptured membranes, or contractions that seem inadequate to explain the advanced effacement and dilation.
Imaging — The cervix may be short (below the 10th percentile [25 mm]), the fetal membranes may be separated, and debris (sludge) may be seen in the amniotic fluid. A rapid rate of decrease in cervical length over time  and cervical shortening before 20 weeks [12-14] may be noted. (See "Second-trimester evaluation of cervical length for prediction of spontaneous preterm birth", section on 'Technique'.)
Laboratory — Uncomplicated cervical insufficiency is not associated with laboratory abnormalities.
In some cases, cervical insufficiency is caused by, or leads to, subclinical intraamniotic infection, which is diagnosed by laboratory examination of amniotic fluid. (See "Intraamniotic infection (chorioamnionitis)", section on 'Diagnosis of clinical chorioamnionitis'.)
Cervicovaginal fetal fibronectin (fFN) may be positive. In asymptomatic women, the combination of a short (≤25 mm) cervix on ultrasound examination and a positive fFN result is predictive of an increased risk of preterm delivery, especially in women with a previous preterm delivery, while two negative tests are reassuring (less than 1 percent chance of preterm delivery in the next week or two) [15-19]. We do not obtain fFN in asymptomatic pregnant women as no intervention is available that will prevent subsequent prelabor labor in asymptomatic fFN positive women.
DIAGNOSIS — We base the diagnosis of cervical insufficiency on either classic historic factors or, preferably, by a combination of historic factors and transvaginal ultrasound (TVU) measurement of cervical length. Physical examination alone is adequate in women with advanced cervical dilation.
●History-based diagnosis of cervical insufficiency – We make a history-based diagnosis of cervical insufficiency in women with ≥two consecutive prior second-trimester pregnancy losses associated with relatively painless early cervical dilation or ≥three early (<34 weeks) preterm births in which other causes of pregnancy loss or preterm birth (eg, infection, placental bleeding, multiple gestation, preterm labor) have been excluded. Risk factors for cervical insufficiency support the diagnosis. (See 'Risk factors' above.)
●History, ultrasound, and physical examination-based diagnosis of cervical insufficiency – We make a diagnosis of cervical insufficiency in women with one or two prior second-trimester pregnancy losses or preterm births and cervical length ≤25 mm on TVU examination or advanced cervical changes on physical examination before 24 weeks of gestation. Risk factors for cervical insufficiency support the diagnosis. (See 'Risk factors' above.)
The diagnosis of cervical insufficiency is usually limited to singleton gestations because the pathogenesis of second-trimester pregnancy loss/preterm delivery in multiple gestations is usually unrelated to a weakened cervix. In addition, preterm labor, infection, abruptio placenta, bleeding placenta previa, and abruptio placentae should be excluded, as these disorders could account for biochemically mediated cervical ripening leading to second-trimester pregnancy loss or preterm delivery independent of structural/anatomic cervical weakness .
The American College of Obstetricians and Gynecologists (ACOG) defines cervical insufficiency as the inability of the uterine cervix to retain a pregnancy in the second trimester in the absence of clinical contractions, labor, or both .
Can cervical insufficiency be diagnosed before pregnancy? — The diagnosis of cervical insufficiency cannot be made or excluded in nonpregnant women by any test. Evaluation of cervical function with dilators, balloons, or hysteroscopy is not helpful. Ultrasound, magnetic resonance imaging (MRI), or hysterosalpingography may reveal a uterine anomaly, which is a risk factor for cervical insufficiency, but is not diagnostic.
APPROACH TO MANAGEMENT — The following approach to management applies to women with singleton pregnancies. Cerclage is not indicated in any twin or other multiple pregnancies, given the body of evidence shows no improvement in pregnancy outcome compared with appropriate controls without cerclage. (See "Twin pregnancy: Prenatal issues", section on 'Unproven interventions to prevent or delay preterm labor'.)
Women with prior pregnancy losses or preterm births
Candidates for history-indicated cerclage — We suggest a history-indicated transvaginal cerclage at 12 to 14 weeks for women with a history-based diagnosis of cervical insufficiency (table 1). (See 'Diagnosis' above.)
A minority of recurrent second-trimester losses/preterm births is primarily, and perhaps exclusively, caused by congenital or acquired structural weakness of the cervix, and can be treated effectively with structural support from a history-indicated cerclage. Anatomical, biochemical, and clinical evidence from observational studies and randomized trials consistently support this approach [22-25].
We also treat these women with hydroxyprogesterone caproate weekly from 16 to 36 weeks of gestation [26-28]. Although randomized trials support the benefit of history-indicated cerclage (25 percent reduction in deliveries <33 weeks)  and the benefit of progesterone supplementation [26-28] in this population, no trials have evaluated the efficacy of combination therapy (both history-indicated cerclage and hydroxyprogesterone caproate).
Candidates for ultrasound surveillance and possible ultrasound-indicated cerclage — The majority of women with suspected cervical insufficiency do not meet criteria for a history-based diagnosis of cervical insufficiency and, in turn, a history-indicated cerclage (see 'Diagnosis' above). For these women, we administer hydroxyprogesterone caproate prophylaxis against preterm delivery, monitor cervical length with transvaginal ultrasound (TVU) (table 2), and apply a cerclage if cervical length is ≤25 mm . The following lines of evidence provide the rationale for this approach:
●In randomized trials, progesterone prophylaxis with hydroxyprogesterone caproate starting at 16 to 20 weeks of gestation in women with a history of spontaneous preterm birth and continuing until 36 weeks reduced the risk of recurrent preterm birth. (See "Progesterone supplementation to reduce the risk of spontaneous preterm birth".)
●Women with a short cervix on TVU examination in the second trimester are at increased risk of spontaneous preterm birth. (See "Second-trimester evaluation of cervical length for prediction of spontaneous preterm birth".)
●Placement of a cerclage upon identification of a short cervix (ultrasound-indicated cerclage) is effective in reducing preterm birth , results in pregnancy outcomes comparable to those with history-indicated cerclage , and avoids cerclage in about 60 percent of patients with a suggestive history . The benefit of ultrasound-indicated cerclage may derive from bolstering cervical strength , preventing membranes from being exposed, and retention of the mucus plug.
•In a 2011 meta-analysis of randomized trials of women with singleton gestation and prior spontaneous preterm birth and short cervical length ≤25 mm before 24 weeks, placement of an ultrasound-indicated cerclage reduced total neonatal morbidity and mortality by over one-third (15.6 versus 24.8 percent without cerclage; RR 0.64, 95% CI 0.45-0.91), presumably because cerclage reduced the frequency of preterm birth by 30 percent (delivery <35 weeks RR 0.70, 95% CI 0.55-0.89; 28.4 percent versus 41.3 percent in women without cerclage) .
•In another 2011 meta-analysis of randomized trials of women with singleton gestations and prior preterm birth managed either by (1) cervical length screening with cerclage for short cervical length or (2) history-indicated cerclage, both groups had similar rates of preterm birth before 37 weeks (31 versus 32 percent, RR 0.97, 95% CI 0.73-1.29), preterm birth before 34 weeks (17 versus 23 percent, RR 0.76, 95% CI 0.48-1.20), and perinatal mortality (5 versus 3 percent, RR 1.77, 95% CI 0.58-5.35) . Only 42 percent of patients in the ultrasound screening group developed a short cervical length and received cerclage versus 100 percent in the history-indicated group.
We usually initiate cervical length screening at about 14 weeks, but may screen as early as 12 weeks in women with early second-trimester losses, recurrent second-trimester losses, or a prior large cold-knife conization (table 2) . In women with prior preterm birth at 28 to 36 weeks, we initiate screening at 16 weeks. Ultrasound examination is generally repeated every two weeks until 24 weeks as long as the cervical length is ≥30 mm, and increased to weekly if cervical length is 25 to 29 mm, with the expectation that preterm cervical changes will precede overt preterm labor or membrane rupture symptoms by three to six weeks . Serial screening was effective in large trials [12,32], but merits further study since a single screen may also be effective . TVU screening is usually discontinued at 24 weeks of gestation, as cerclage is rarely performed after this time. (See "Second-trimester evaluation of cervical length for prediction of spontaneous preterm birth".)
We continue intramuscular hydroxyprogesterone caproate supplementation until 36 weeks, whether or not a cerclage is placed. Although no studies have reported a statistically significant improvement in pregnancy outcome with combined therapy [32,36,37], these studies are retrospective analyses and underpowered. One post-hoc analysis of data from a randomized trial observed that the rate of early preterm birth trended lower in women who received both hydroxyprogesterone caproate and ultrasound-indicated cerclage than in those who received either therapy alone (preterm birth <28 weeks: both interventions: 9 percent versus cerclage alone: 17 percent and progesterone alone: 15 percent; preterm birth <32 weeks: both interventions: 17 percent versus cerclage alone: 25 percent and progesterone alone: 21 percent) .
No randomized trial has directly compared vaginal progesterone, intramuscular hydroxyprogesterone caproate, and cervical cerclage for the prevention of preterm birth in women with a sonographic short cervix in the midtrimester, singleton gestation, and previous preterm birth. An indirect comparison meta-analysis concluded vaginal progesterone and cerclage were equally efficacious in the prevention of preterm birth in this population . Based on evidence from the direct comparisons in the randomized trials discussed above, we treat women with prior preterm birth with intramuscular hydroxyprogesterone caproate and then perform cerclage if the cervical length becomes ≤25 mm. (See 'Women with prior pregnancy losses or preterm births' above.)
An alternative approach is to substitute vaginal progesterone for intramuscular hydroxyprogesterone caproate in women with a history of preterm birth who develop a short cervix. Some clinicians perform an amniocentesis to assess for subclinical infection before placing a cerclage in women with a short cervix.
Women with no prior preterm birth, but risk factors for cervical insufficiency — Although these women may develop cervical insufficiency, the pregnancy course and outcome need to be evaluated before making this diagnosis. We perform a single TVU cervical length measurement at 18 to 24 weeks in women with no prior preterm birth but risk factors for cervical insufficiency (table 2), and treat those with a short cervix (≤20 mm) with vaginal progesterone supplementation. Administration of vaginal progesterone to women with a short cervix reduces the rate of spontaneous preterm birth and composite neonatal morbidity and mortality and appears to be cost-effective. The evidence supporting this approach, including the rationale for the 20 mm threshold for defining a short cervix, is reviewed separately. (See "Second-trimester evaluation of cervical length for prediction of spontaneous preterm birth", section on 'Guidelines for cervical length screening and intervention' and "Progesterone supplementation to reduce the risk of spontaneous preterm birth", section on 'Short cervix in current pregnancy'.)
If the patient delivers preterm, subsequent pregnancies are managed as described above (see 'Women with prior pregnancy losses or preterm births' above), and may warrant an ultrasound-indicated cerclage if cervical length is ≤25 mm. If she delivers at term, we again perform a single cervical length measurement at 18 to 24 weeks and give vaginal progesterone if the cervix is short.
Physical examination reveals a dilated cervix and visible membranes before 24 weeks — Rarely, a woman presents before 24 weeks with minimal or no symptoms and physical examination reveals a dilated cervix. Occasionally, such findings follow the identification of a very short cervical length (eg, <5 mm) on TVU examination.
We consider physical examination-indicated cerclage a reasonable option for these women, in the absence of overt infection, labor, ruptured membranes, or significant hemorrhage (eg, abruption), since these conditions would likely make delivery within hours or a few days inevitable. Other options include expectant management and, where legal, pregnancy termination. In a systematic review including a small randomized trial, two prospective cohort studies, and seven retrospective cohort studies, placement of a "physical examination-indicated cerclage" (also called "rescue cerclage" or "emergency cerclage") in patients with a dilated cervix and visible membranes on digital examination in the second trimester appeared to improve pregnancy outcome compared with no cerclage (neonatal survival 71 percent with cerclage versus 43 percent with expectant management; RR 1.65, 95% CI 1.19-2.28) . The mean age at diagnosis in the cerclage and expectant management groups was 21.7 and 22.8 weeks of gestation, respectively; the mean time to delivery was 57 and 19 days, respectively; and the mean gestational age at delivery was 30.6 and 25.2 weeks, respectively. Although these largely observational data are low-quality evidence, the analysis is the best available evidence to inform decision-making in this setting.
We perform amniocentesis to look for subclinical infection when the cervix is ≥2 cm dilated and on a case-by-case basis when ultrasound findings are consistent with inflammation (eg, debris in the amniotic fluid ["sludge"] (image 1)). We do not perform cerclage if we find evidence of subclinical infection as these pregnancies are at increased risk of preterm delivery and other pregnancy complications [41-44]. (See "Intraamniotic infection (chorioamnionitis)", section on 'Amniocentesis' and "Second-trimester evaluation of cervical length for prediction of spontaneous preterm birth".)
Prior successful outcome after cerclage — We suggest TVU cervical length screening in future pregnancies for women who received an ultrasound-indicated cerclage in a prior pregnancy and had a successful outcome. The risk of preterm birth in future pregnancies does not warrant routine placement of a cerclage , but if ultrasound surveillance shows a short cervix in a subsequent pregnancy, we place another cerclage. In one study, only 50 percent of women with a history of an ultrasound-indicated cerclage required another ultrasound-indicated cerclage in the subsequent pregnancy, and their outcomes were similar to those who underwent planned cerclage in the subsequent pregnancy .
Successful pregnancy outcome after ultrasound-indicated cerclage does not establish a diagnosis of cervical insufficiency as a substantial proportion of pregnancies with premature cervical effacement have good outcomes in the index pregnancy and future pregnancies in the absence of surgical intervention. This is particularly true in women who, after removal of the cerclage at 36 to 37 weeks, do not go into labor in the next two weeks.
Prior unsuccessful outcome after cerclage — Transabdominal cerclage may be successful in women who deliver very preterm despite placement of a transvaginal cerclage. (See "Transabdominal cervical cerclage".)
Pessary — Vaginal pessaries are intended to alter the axis of the cervical canal and displace the weight of the uterine contents away from the cervix. By changing the angle of the cervix in relation to the uterus, the pessary also obstructs the internal os and thus may provide protection against ascending infection.
We do not prescribe pessaries for women with a short cervix. The body of evidence does not support using a pessary to prolong gestation or improve neonatal outcome; however, further study is warranted as the available evidence is limited by differences in use of progesterone prophylaxis among the trials, the small number of preterm births and neonatal complications, and lack of patient/clinician blinding.
In 2012, a multicenter randomized trial of pregnant women with singleton pregnancies and cervical length ≤25 mm at 20 to 23 weeks reported an 80 percent reduction in spontaneous preterm birth in the group assigned to use of a cervical pessary compared with the group assigned to expectant management (preterm birth <34 weeks: 12/190 [6 percent] versus 51/190 [27 percent]) . A randomized trial in twin pregnancies with a short cervix reported a 60 percent reduction in spontaneous preterm birth <34 weeks (11/68 [16 percent] versus 26/66 [39 percent]) . In contrast, two subsequent similarly designed randomized trials in singleton pregnancies did not confirm efficacy [49,50]. In the largest of these trials (n = 932 participants), no differences in rates of spontaneous preterm birth <34 weeks (55/460 [12 percent] versus 50/464 [10.8 percent]), perinatal death, adverse neonatal events, or neonatal special care were noted between the pessary and control (no pessary) groups . Because of slow recruitment, the trial was terminated before the planned 1600 women underwent randomization. In all of the trials, vaginal discharge was the major side effect of using a pessary.
Indomethacin — A review of data from three randomized cerclage trials found that indomethacin therapy for asymptomatic women with a short cervix (≤25 mm) at 14 to 27 weeks who did not receive a cerclage did not reduce spontaneous preterm births <35 weeks, but appeared to reduce preterm births <24 weeks . Further research including a larger number of pregnancies and a randomized trial design is necessary to further clarify the effectiveness, as well as the risks, of this therapy.
Antibiotics — There is insufficient evidence to recommend antibiotics for women with cervical insufficiency, based on poor obstetrical history, short transvaginal ultrasound (TVU) cervical length, or dilated cervix on physical examination.
Lifestyle interventions — Clinicians should consider the available evidence and the patient's individual circumstances when making lifestyle recommendations as there are social, psychological, financial, and medical side effects associated with these interventions. Lifestyle interventions (cessation of work and exercise, abstinence from coitus, bedrest/limited activity) have not been adequately evaluated by well-designed studies. Although coitus is not a risk factor for onset of labor in women at term who are scheduled for induction , there are inadequate data on the safety of coitus in women at risk for preterm birth because of previous preterm birth or preterm cervical ripening . In our practice, we advise women with both a prior preterm birth and a short cervix to avoid coitus.
SUMMARY AND RECOMMENDATIONS — The following algorithm summarizes the author's approach (algorithm 1).
●Cervical insufficiency describes a presumed physical weakness of cervical tissue that causes or contributes to the early delivery of an otherwise healthy pregnancy, usually in the second trimester. (See 'Introduction' above.)
●Cervical insufficiency may be congenital or acquired. Women at risk include those with a history of cervical trauma, collagen disorders, or congenital anomalies of the uterus/cervix. (See 'Risk factors' above.)
●The diagnosis of cervical insufficiency is either based on historic factors or on a combination of historic factors and transvaginal ultrasound (TVU) measurement of cervical length. (See 'Diagnosis' above.)
•History-based diagnosis of cervical insufficiency – We make a history-based diagnosis of cervical insufficiency in women with ≥two consecutive prior second-trimester pregnancy losses associated with relatively painless early cervical dilation or ≥three early (<34 weeks) preterm births in which other causes of pregnancy loss or preterm birth (eg, infection, placental bleeding, multiple gestation, preterm labor) have been excluded. Risk factors for cervical insufficiency support the diagnosis. (See 'Risk factors' above.)
•History, ultrasound, and physical examination-based diagnosis of cervical insufficiency – We make a diagnosis of cervical insufficiency in women with one or two prior second-trimester pregnancy losses or preterm births and cervical length ≤25 mm on TVU examination or advanced cervical changes on physical examination before 24 weeks of gestation. Risk factors for cervical insufficiency support the diagnosis. (See 'Risk factors' above.)
Women with singleton pregnancies
●For women with history-based diagnosis of cervical insufficiency, we recommend history-indicated cerclage rather than ultrasound monitoring of cervical length (Grade 1B). (See 'Candidates for history-indicated cerclage' above.)
●For women with suspected cervical who do not meet criteria for history-indicated cerclage, sonographic surveillance should be started early in pregnancy (eg, 14 to 16 weeks). We suggest cerclage for women who develop a short cervix (≤25 mm) before 24 weeks (Grade 2B) (see 'Candidates for ultrasound surveillance and possible ultrasound-indicated cerclage' above). Vaginal progesterone administration is an alternative approach. We suggest not placing a pessary (Grade 2C). (See "Progesterone supplementation to reduce the risk of spontaneous preterm birth", section on 'Short cervix in current pregnancy' and 'Pessary' above.)
●For women with a grossly dilated cervix and visible membranes on digital examination at <24 weeks and no labor or signs of infection, we suggest a physical exam-indicated cerclage rather than expectant management (Grade 2C). (See 'Physical examination reveals a dilated cervix and visible membranes before 24 weeks' above.)
●We recommend progesterone supplementation for women with a history of spontaneous preterm birth (Grade 1B). (See "Progesterone supplementation to reduce the risk of spontaneous preterm birth".)
Women with multiple gestations
●For women with twin or higher order multiple pregnancies, we suggest avoiding cerclage (Grade 2C). (See "Twin pregnancy: Prenatal issues", section on 'Unproven interventions to prevent or delay preterm labor'.)
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