INTRODUCTION — Cervical insufficiency can be defined as recurrent painless cervical dilation leading to second-trimester pregnancy losses. The American College of Obstetricians and Gynecologists' definition is "the inability of the uterine cervix to retain a pregnancy in the second trimester in the absence of clinical contractions, labor, or both" [1]. Although it may occur in a single pregnancy, the diagnosis is confirmed when it recurs in consecutive pregnancies.
This topic will review issues related to diagnosis and management of patients with cervical insufficiency. Issues related to cerclage procedures for treatment of cervical insufficiency are discussed separately. (See "Transvaginal cervical cerclage" and "Transabdominal and laparoscopic cervicoisthmic cerclage".)
PATHOGENESIS — Structural cervical weakness is the likely cause of many recurrent second-trimester losses and live births. The weakness may be secondary to prior cervical or uterine surgery (eg, dilation and curettage, hysteroscopy) or, rarely, a congenital abnormality.
Second-trimester births/losses can also be associated with decidual inflammation/infection, bleeding at the interface of the decidua and placenta, or uterine overdistension. These other disorders can initiate biochemical changes in the cervix that lead to premature cervical shortening and often a single (ie, nonrecurrent) second-trimester birth/loss. (See "Spontaneous preterm birth: Pathogenesis".)
CLINICAL FINDINGS
Past history — The classic obstetric history of patients with structural cervical weakness leading to recurrent cervical insufficiency is characterized by all of the following:
●Recurrent second-trimester pregnancy losses or live births, often before 24 weeks of gestation
●No or minimal mild symptoms (see 'Symptoms' below)
●Cervical dilation and effacement on physical examination inconsistent with the degree of uterine activity (no or minimal contractions)
In addition, the duration from recognition of symptoms/physical findings to delivery may have been extremely short, and successive pregnancies may have been associated with progressively earlier gestational age at loss or live birth.
Risk factors — Cervical abnormalities are a risk factor for structural cervical weakness and, in turn, recurrent cervical insufficiency.
●Cervical trauma – Cervical trauma is most common risk factor for cervical insufficiency. It may result from the process of labor or birth (spontaneous, forceps- or vacuum-assisted, cesarean) [2], rapid mechanical cervical dilation before a gynecologic procedure, or treatment of cervical intraepithelial neoplasia. (See "Overview of pregnancy termination", section on 'Future pregnancies' and "Reproductive effects of cervical excisional and ablative procedures".)
●Congenital cervical abnormalities – Congenital abnormalities are rarely associated with structural cervical weakness. These abnormalities include genetic disorders affecting collagen (eg, Ehlers-Danlos syndrome) [3-5], uterine anomalies, in utero diethylstilbestrol exposure, and biologic variation. (See "Congenital uterine anomalies: Clinical manifestations and diagnosis" and "Outcome and follow-up of diethylstilbestrol (DES) exposed individuals", section on 'Pregnancy loss and preterm birth'.)
●History of short cervical length – In contemporary obstetrics, where cervical length (CL) screening is often performed, patients may describe a past pregnancy or pregnancies in which a short CL was detected on ultrasound and was associated with subsequent second-trimester loss/birth. The finding of a short second-trimester CL on transvaginal ultrasound examination alone is not a strong risk factor for cervical insufficiency as many patients with a short CL deliver at term even without intervention. (See "Short cervix before 24 weeks: Screening and management in singleton pregnancies".)
Symptoms — Patients with cervical insufficiency in the current pregnancy may be asymptomatic or may present with mild symptoms, such as:
●Pelvic pressure
●Braxton-Hicks-like contractions
●Premenstrual-like cramping and/or backache
●Change in vaginal discharge. Discharge volume may increase; the color may change from clear, white, or light yellow to pink, tan, or red spotting; and the consistency may become thinner.
Symptoms, if present, typically begin between 14 and 20 weeks of gestation and may be present for several days or weeks before the diagnosis of cervical insufficiency is made.
Physical examination — Early in the course of cervical insufficiency, the cervix may be soft and closed, with minimal effacement [6]. Tocodynamometry typically reveals no or infrequent contractions at irregular intervals. Provocative maneuvers such as suprapubic or fundal pressure by the clinician or having the patient make a forced expiratory effort against a closed glottis (Valsalva maneuver) may reveal fetal membranes in the endocervical canal or vagina, which is always an abnormal finding. In some cases, membranes may be prolapsed without provocation or may be ruptured.
Imaging — On transvaginal ultrasound, CL is typically short (≤25 mm) and debris (sludge [fetal squames, vernix, leukocytes, bacteria] or biofilm) may be seen in the amniotic fluid. If serial ultrasound examinations are performed, CL may decrease over time [7].
Laboratory — Uncomplicated cervical insufficiency is not associated with laboratory abnormalities.
DIAGNOSIS — We make the diagnosis of cervical insufficiency in any of the following settings:
●A classic past obstetric history (See 'Obstetric history-based diagnosis' below.)
●A combination of obstetric history of second-trimester loss or extremely preterm live birth (<28 weeks) plus a short cervix on transvaginal ultrasound (TVU) examination in the current pregnancy (see 'Ultrasound-based diagnosis' below) and after exclusion of relevant other diagnoses (see 'Diagnoses to exclude before making the diagnosis' below)
●Physical examination showing advanced cervical dilation and/or effacement in the absence of labor (see 'Physical examination-based diagnosis' below) and after exclusion of relevant other diagnoses (see 'Diagnoses to exclude before making the diagnosis' below)
The diagnosis is usually limited to singleton gestations because the pathogenesis of second-trimester pregnancy loss or live birth in multiple gestations is usually unrelated to a weakened cervix.
Obstetric history-based diagnosis — We make an obstetric history-based diagnosis of cervical insufficiency in patients with a classic history of ≥2 consecutive prior second-trimester pregnancy losses or extremely preterm births (<28 weeks) associated with no or minimal mild symptoms. The presence of risk factors for structural cervical weakness supports the diagnosis. Most of these cases are pregnancy losses before 24 weeks. (See 'Past history' above.)
Challenges to making this diagnosis are that the relevant findings in the prior pregnancy are often not well-documented in medical records and the patient's recounting of events may not provide adequate information; thus, the process that led to the second trimester loss or extremely preterm birth is often a subjective assessment.
Ultrasound-based diagnosis — In asymptomatic patients with a past history of one extremely preterm birth associated with no or minimal mild symptoms (see 'Symptoms' above) and those in whom a history-based diagnosis is uncertain, we perform serial TVU examinations and make a diagnosis of cervical insufficiency when CL is ≤25 mm before 24 weeks (algorithm 1); labor, infection, and bleeding related to placental abruption or placenta previa should be excluded (see 'Diagnoses to exclude before making the diagnosis' below). The presence of risk factors for structural cervical insufficiency supports the diagnosis (see 'Past history' above). TVU screening is discontinued at 24 weeks of gestation, as cerclage is rarely performed after this gestational age [8].
This approach is supported by a meta-analysis of randomized trials of patients with singleton gestations and prior preterm birth managed by (1) CL screening with cerclage for short CL or (2) obstetric history-indicated cerclage [9]. Both groups had similar rates of preterm birth before 37 weeks (31 versus 32 percent, relative risk [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). In the ultrasound screening group, only 42 percent of patients developed a short CL and received cerclage whereas, in the history-indicated group, 100 percent of patients received a history-indicated cerclage. Based on these and other data, in patients with a history suggestive of cervical insufficiency, placement of a cerclage upon identification of a short cervix on ultrasound is effective in reducing preterm birth [10], results in pregnancy outcomes comparable to history-indicated cerclage [9], and avoids cerclage in approximately 60 percent of patients [9].
If a patient in this population develops symptoms of cervical insufficiency (see 'Symptoms' above) between cervical screening examinations, an ultrasound examination for CL should be performed promptly because a normal physical examination cannot reliably exclude the diagnosis of cervical insufficiency. Most cervixes that are 10 to 25 mm in length by second-trimester TVU feel long and closed on physical examination; effacement and dilation are usually not detected until the transvaginal CL is ≤10 mm. In one study, less than one-third of patients with CL <11 mm had cervical dilation ≥1 cm on physical examination [11].
Physical examination-based diagnosis — We make a diagnosis of physical examination-based cervical insufficiency in patients at 14 to 27 weeks of gestation with a dilated and effaced cervix on physical examination and no contractions or weak irregular contractions that appear inadequate to explain the cervical dilation and effacement. The membranes may be prolapsed or ruptured. Labor, infection, and bleeding related to placental abruption or placenta previa should be excluded. (See 'Diagnoses to exclude before making the diagnosis' below.)
Diagnoses to exclude before making the diagnosis
●Labor should be excluded by tocodynamometry. (See "Preterm labor: Clinical findings, diagnostic evaluation, and initial treatment".)
●Infection should be excluded by appropriate studies, such as urinalysis/urine culture and possibly amniocentesis. Subclinical intraamniotic infection is diagnosed by laboratory examination of amniotic fluid. In patients with an ultrasound-based diagnosis, amniocentesis is not routinely performed as most patients do not have significant cervical dilation, prolapsed membranes, or abnormal-appearing amniotic fluid. In patients with a physical examination-based diagnosis, amniocentesis is often indicated since many patients have significant cervical dilation, prolapsed membranes, or abnormal-appearing amniotic fluid. (See 'Candidates for amniocentesis' below.)
●Bleeding from placental abruption or placenta previa should be excluded by history and physical and ultrasound examination as these disorders could account for biochemically mediated cervical ripening leading to second-trimester pregnancy loss or preterm delivery independent of structural cervical weakness [12]. (See "Preterm labor: Clinical findings, diagnostic evaluation, and initial treatment" and "Acute placental abruption: Pathophysiology, clinical features, diagnosis, and consequences" and "Placenta previa: Epidemiology, clinical features, diagnosis, morbidity and mortality".)
Candidates for amniocentesis — We perform amniocentesis to look for subclinical infection:
●Routinely, when the cervix is ≥2 cm dilated on digital or speculum examination, as the incidence of intraamniotic infection in these patients is approximately 20 to 50 percent [13]
●On a case-by-case basis, when:
•Ultrasound findings are consistent with inflammation (eg, debris in the amniotic fluid [sludge or biofilm] (image 1))
•Membranes are visible and exposed at the external os, but the cervix is <2 cm dilated.
In these settings, the incidence of intraamniotic infection is probably no more than 5 to 10 percent.
Management of patients with subclinical infection on amniocentesis — We do not perform cerclage if we find evidence of infection after testing amniotic fluid, as these pregnancies are at increased risk of preterm birth and other pregnancy complications [14-17]. We do not give antibiotics in an attempt at expectant management and continuation of pregnancy; we recommend induction.
The safety and effectiveness of antibiotic treatment in these patients have not been evaluated extensively. In the largest study, which included 22 patients with painless cervical dilation >1 cm between 16.0 and 27.9 weeks, intact membranes, no uterine contractions, and evidence of intraamniotic inflammation (19/22) or infection (3/22) on amniocentesis, administration of triple antibiotic treatment (ceftriaxone, clarithromycin, and metronidazole) was associated with delivery more than one week after amniocentesis in 16 patients (73 percent), and no cases of serious maternal morbidity were reported [18]. Twelve patients received a cerclage. Importantly, 9 of the 12 patients who underwent repeat amniocentesis had objective evidence of resolution of intraamniotic infection/inflammation. Of the three with intraamniotic infection on initial amniocentesis, two had positive amniotic fluid cultures and delivered within a week, whereas the third only had a positive polymerase chain reaction (PCR) for Ureaplasma species. This patient had a negative PCR at repeat amniocentesis three weeks later, despite membrane rupture a week after the initial amniocentesis. She was induced at 34 weeks with good neonatal outcome. Given that the pathogenicity of Ureaplasma in amniotic fluid is unclear and no patients with a positive amniotic fluid culture gained more than a week despite antibiotics, the safety and effectiveness of expectant management with antibiotic therapy remain unproven. (See "Intraamniotic infection (clinical chorioamnionitis)", section on 'When to perform amniocentesis to test amniotic fluid'.)
Can cervical insufficiency be diagnosed before pregnancy? — The diagnosis of cervical insufficiency cannot be made or excluded in nonpregnant patients by any test. Evaluation of cervical function with dilators, balloons, or hysteroscopy is not helpful. Ultrasound, magnetic resonance imaging, or hysterosalpingography may reveal a uterine anomaly, which is a risk factor for cervical insufficiency, but is not diagnostic. (See "Congenital uterine anomalies: Clinical manifestations and diagnosis".)
CERCLAGE PLACEMENT AND USE OF PROGESTERONE SUPPLEMENTATION — The following approach to management applies to patients with singleton pregnancies. Pretreatment evaluation was reviewed above. (See 'Diagnoses to exclude before making the diagnosis' above.)
Obstetric history-based cervical insufficiency
●Cerclage – We suggest cerclage placement (called a history-indicated cerclage) at 12 to 14 weeks of gestation in patients with recurrent (more than one) second-trimester losses preceded by painless cervical dilatation. Structural weakness of the cervix can be treated effectively with structural support from a cerclage. Anatomical, biochemical, and clinical evidence from observational studies and randomized trials consistently support this approach [19-22].
●Supplemental progesterone – At 16 weeks of gestation, the author also begins progesterone supplementation with either hydroxyprogesterone caproate weekly or vaginal progesterone daily and continues progesterone until 36+6 weeks of gestation. The choice of progesterone supplement is made by the patient after discussion of data about both preparations.
The author's use of progesterone supplementation in patients with a history-indicated cerclage is based on the data of efficacy in patients with a previous preterm birth. (See "Progesterone supplementation to reduce the risk of spontaneous preterm labor and birth".)
The routine use of progesterone supplementation in patients with a history-indicated cerclage is controversial, in part because no randomized trials have evaluated the efficacy of combination therapy (both history-indicated cerclage and progesterone supplementation) these patients. In a systematic review of five observational studies (546 participants) evaluating progesterone supplementation is this population, combination therapy was not associated with a reduction in spontaneous recurrent preterm birth or improvement in perinatal outcomes compared with cerclage alone [23]. (See "Progesterone supplementation to reduce the risk of spontaneous preterm labor and birth", section on 'Choice of progesterone preparation and dose'.)
Ultrasound-based cervical insufficiency
●Cerclage – We suggest cerclage placement (called ultrasound-indicated cerclage) in patients with one prior spontaneous preterm birth and TVU CL ≤25 mm before 24 weeks in the current pregnancy. A meta-analysis of randomized trials found that placement of a cerclage in this setting reduced preterm birth <24, 28, 32, 35, and 37 weeks (eg, relative risk for birth <35 weeks: 0.70, 95% CI 0.55-0.89) [10].
●Supplemental progesterone – For patients with a prior spontaneous preterm birth, the author prescribes hydroxyprogesterone caproate or vaginal progesterone beginning at 16 (optimal) to 20 weeks of gestation (which may be before or after cerclage placement) and continues it through 36+6 weeks. As discussed above, the choice of progesterone supplement is made by the patient after discussion of data about both preparations. (See 'Obstetric history-based cervical insufficiency' above.)
In a systematic review of four observational studies (396 participants) evaluating cerclage alone versus cerclage plus hydroxyprogesterone caproate in patients with an ultrasound-indicated cerclage, combination therapy was not associated with a reduction in spontaneous recurrent preterm birth or improvement in perinatal outcome, but there were trends for benefit for preterm birth <28 and <24 weeks [24]. As above, given the limitations of small observational studies, continuation of progesterone supplementation in this setting is neither well supported nor refuted by available data.
Another alternative approach is to treat these patients with vaginal progesterone alone, without cerclage placement. The author does not advise this approach because a meta-analysis of randomized trials found that placement of a cerclage upon identification of a short cervix is effective in reducing preterm birth compared with no cerclage [10], whereas the only evidence that vaginal progesterone alone may be as effective as cerclage is an indirect meta-analysis of randomized trials, in which the two groups were not similar in several characteristics and the cerclage group was at higher risk for preterm birth [25].
Physical examination-based cervical insufficiency
●Cerclage – For patients with physical examination-based cervical insufficiency before 24 weeks of gestation, we consider cerclage placement a reasonable option (preferably called physical examination-indicated cerclage; also called rescue or emergency cerclage).
•In a meta-analysis including a small randomized trial, two prospective cohort studies, and seven retrospective cohort studies, placement of a "physical examination-indicated cerclage" appeared to improve pregnancy outcome compared with no cerclage (neonatal survival 71 percent with cerclage versus 43 percent with expectant management, relative risk 1.65, 95% CI 1.19-2.28) [26]. 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 after diagnosis was 57 and 19 days, respectively; the mean difference in pregnancy prolongations was 34 days; and the mean gestational age at delivery was 30.6 and 25.2 weeks, respectively. Birth at all preterm gestations was reduced except those prior to 24 weeks.
•A similar meta-analysis found that physical examination-indicated cerclage was superior to expectant management for reducing preterm birth before 28 and 32 gestational weeks [27].
•Although these largely observational data are low-quality evidence, the analyses are the best available evidence to inform decision-making in this setting.
Most clinicians avoid placing a cerclage after approximately 24 weeks of gestation since the procedure may cause accidental rupture of the fetal membranes leading to early preterm delivery of a viable infant, with its attendant high risk of neonatal morbidity and mortality. However, each case must be individualized, weighing the risks of the procedure against the likely outcome with expectant management. (See "Periviable birth (limit of viability)".)
●Progesterone supplementation – The author's practice is to continue progesterone supplementation post-cerclage in patients who had been on the drug pre-cerclage because of a previous preterm birth. For patients with no history of previous preterm birth, the author begins vaginal progesterone post-cerclage.
Cerclage procedure — The cerclage procedure, potential complications, post-operative care and follow-up, and outcome are described separately. (See "Transvaginal cervical cerclage".)
MANAGEMENT OF SPECIAL POPULATIONS
Patients with no prior second-trimester pregnancy loss or extremely preterm birth, but risk factors for cervical insufficiency — Although a minority of these patients develop cervical insufficiency, most do not; therefore, we believe the current pregnancy course and outcome need to be evaluated before making the diagnosis of cervical insufficiency. The author performs a single transvaginal cervical length (CL) measurement at 18 to 24 weeks of gestation (usually at approximately 20 weeks, with the anatomic survey ultrasound) in this population, and treats those with a short cervix in the same way as other patients without a history of preterm birth who develop a short cervix. (See "Short cervix before 24 weeks: Screening and management in singleton pregnancies", section on 'Nulliparous patients and parous patients with no prior spontaneous preterm singleton birth'.)
Patients with no prior preterm birth but a short cervix — Patients with singleton pregnancies and no history of preterm birth who develop a short cervix are treated with vaginal progesterone. Placement of a cerclage may be helpful in those with transvaginal ultrasound CL <10 mm. These data and approaches to this population are reviewed separately. (See "Short cervix before 24 weeks: Screening and management in singleton pregnancies", section on 'Nulliparous patients and parous patients with no prior spontaneous preterm singleton birth'.)
Multiple gestations — The body of evidence does not support the efficacy of routine cerclage in multiple gestations, but it may be useful in patients with a classical history of cervical insufficiency or a short cervix. These data are reviewed separately. (See "Twin pregnancy: Management of pregnancy complications", section on 'Patient selection for cerclage' and "Triplet pregnancy", section on 'Unproven interventions'.)
ADJUNCTIVE BEHAVIORAL COUNSELING — Lifestyle interventions (cessation of work and exercise, abstinence from coitus, bedrest/limited activity) have not been adequately evaluated by well-designed studies. 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.
In our practice, we advise patients with an obstetric history-based diagnosis of cervical insufficiency to continue their normal daily activities, with no restrictions other than those given to healthy pregnant patients.
In patients with an ultrasound-based or physical examination-based diagnosis of cervical insufficiency, we counsel about the option to avoid coitus. Although coitus has been shown not to promote the onset of labor in patients at term who are scheduled for induction [28], there are inadequate data on the safety of coitus in patients at risk for preterm birth because of previous preterm birth or preterm cervical ripening [29]. We advise these patients to continue their normal daily activities, with no restrictions other than those given to healthy pregnant patients. Activity restriction in patients with a short transvaginal ultrasound (TVU) CL has been associated with an increase in preterm birth compared with no activity restriction [30].
INEFFECTIVE AND UNPROVEN INTERVENTIONS
Pessary — We do not prescribe pessaries for patients with a short cervix. In meta-analyses of randomized trials comparing use of a cervical pessary with standard care (no pessary) in asymptomatic patients at high risk for preterm birth (eg, cervical length (CL) ≤25 mm), pessary use did not reduce spontaneous preterm birth <28, 34, or 37 weeks or improve perinatal outcome [31,32].
The theory behind use of vaginal pessaries is that they 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.
MANAGEMENT OF FUTURE PREGNANCIES FOLLOWING CERCLAGE IN INDEX PREGNANCY
Prior successful outcome after cerclage
●Prior successful obstetric history-indicated cerclage – We usually suggest repeat history-indicated cerclage for these patients. If the indication for the initial prior history-indicated cerclage was not evidence based, patients can be counseled that the alternative of serial cervical length (CL) screening can be safe and effective as well [33].
●Prior successful ultrasound-indicated cerclage – We suggest transvaginal ultrasound CL screening in future pregnancies for patients who received an ultrasound-indicated cerclage in a prior pregnancy and had a successful outcome (delivery at or after 34 weeks). The absolute risk of preterm birth in future pregnancies does not warrant routine placement of a cerclage [34], but if ultrasound surveillance shows a short cervix in a subsequent pregnancy, then we place another cerclage. In one study, approximately 50 percent of patients 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 [35].
Successful pregnancy outcome after ultrasound-indicated cerclage does not establish or exclude a diagnosis of cervical insufficiency. 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 patients 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
●Prior unsuccessful obstetric-history indicated cerclage – We offer transabdominal or laparoscopic cervicoisthmic cerclage to patients who fail to deliver a healthy newborn after placement of a history-indicated cerclage. (See "Transabdominal and laparoscopic cervicoisthmic cerclage".)
●Prior unsuccessful ultrasound-indicated cerclage – For patients with a prior ultrasound-indicated cerclage who went on to have an early spontaneous delivery (eg, <34 weeks), we generally suggest an obstetric history-indicated transvaginal cerclage at 12 to 14 weeks of gestation in the next pregnancy because these patients always develop a short CL in subsequent pregnancies [35]. If the obstetric history-indicated cerclage is also unsuccessful, then we offer transabdominal or laparoscopic cervicoisthmic cerclage in a subsequent pregnancy. (See "Transabdominal and laparoscopic cervicoisthmic cerclage".)
SUMMARY AND RECOMMENDATIONS
●Diagnosis – We base the diagnosis of cervical insufficiency on either a classic obstetric history or on a combination of obstetric history and transvaginal ultrasound (TVU) measurement of cervical length (CL). Physical examination alone is adequate for diagnosis of cervical insufficiency in patients with advanced cervical dilation. The diagnosis is usually limited to singleton gestations because the pathogenesis of second-trimester pregnancy loss/extremely preterm delivery (ie, <28 weeks) in multiple gestations is usually unrelated to a weakened cervix. (See 'Diagnosis' above.)
•Obstetric history-based diagnosis of cervical insufficiency – We make an obstetric history-based diagnosis of cervical insufficiency in patients with a classic history of ≥2 consecutive prior second-trimester pregnancy losses/extremely preterm births (ie, <28 weeks) associated with no or minimal mild symptoms. The presence of risk factors for structural cervical weakness support the diagnosis. Most of these cases are pregnancy losses before 24 weeks. Using this diagnostic approach, all of these patients will be offered a history-indicated cerclage. (See 'Obstetric history-based diagnosis' above.)
•Ultrasound-based diagnosis of cervical insufficiency – In asymptomatic patients with a past history of a spontaneous preterm birth associated with no or minimal mild symptoms (see 'Symptoms' above) and those in whom a history-based diagnosis is uncertain, we perform serial TVU examinations and make a diagnosis of cervical insufficiency when CL is ≤25 mm before 24 weeks (algorithm 1). TVU screening is discontinued at 24 weeks of gestation as cerclage efficacy has not been adequately studied after this time. The presence of risk factors for structural cervical insufficiency supports the diagnosis. Using this diagnostic approach, approximately 40 percent of these patients will be offered a cerclage. (See 'Ultrasound-based diagnosis' above.)
•Physical examination-based cervical insufficiency – We make a diagnosis of physical examination-based cervical insufficiency in patients at 14 to 27 weeks of gestation with a dilated and effaced cervix on physical examination and no contractions or weak irregular contractions that appear inadequate to explain the cervical dilation and effacement. The membranes may be prolapsed or ruptured. Most patients <24 weeks of gestation will be offered cerclage (in the absence of contraindications such as infection, [often evaluated by amniocentesis] or rupture of membranes). After 24 weeks, each case must be individualized, weighing the risks of the procedure against the likely outcome with expectant management since the procedure may cause accidental rupture of the fetal membranes leading to early preterm delivery of a viable infant, with its attendant high risk of neonatal morbidity and mortality. (See 'Physical examination-based diagnosis' above.)
●Precerclage amniocentesis (See 'Candidates for amniocentesis' above.)
•We perform amniocentesis to look for subclinical infection before cerclage when the cervix is ≥2 cm dilated on manual or speculum examination, as the incidence of intraamniotic infection in these patients is approximately 20 to 50 percent. We also perform amniocentesis on a case-by-case basis when ultrasound findings are consistent with inflammation (eg, debris in the amniotic fluid [sludge or biofilm] (image 1)) or when membranes are visible and exposed at the external os, as prolapsed membranes are associated with a poor perinatal prognosis.
•We do not perform cerclage if we find evidence of infection on amniocentesis, as these pregnancies are at increased risk of preterm delivery and other pregnancy complications and do not benefit from cerclage.
●Treatment
•For patients with history-based diagnosis of cervical insufficiency, we recommend history-indicated cerclage at 12 to 14 weeks of gestation rather than ultrasound monitoring of CL (Grade 1B). The author also treats these patients with progesterone supplementation weekly from 16 to 36 weeks of gestation. (See 'Obstetric history-based cervical insufficiency' above.)
•For patients with an ultrasound-based diagnosis of cervical insufficiency (both prior spontaneous preterm birth and TVU CL ≤25mm before 24 weeks in the index pregnancy), we suggest ultrasound-indicated cerclage (Grade 2B). For patients with a prior spontaneous preterm birth, the author prescribes progesterone supplementation beginning at 16 (optimal) to 20 weeks of gestation (which is usually before cerclage placement) and continued through 36 weeks. (See 'Ultrasound-based cervical insufficiency' above.)
•For patients with a physical examination-based diagnosis of cervical insufficiency (eg, cervix dilated on speculum or manual digital examination before 24 weeks), we suggest physical examination-indicated cerclage rather than expectant management after consideration for an amniocentesis to rule out intraamniotic infection (Grade 2C). (See 'Physical examination-based cervical insufficiency' above.)
●Multiple gestations – For patients with twin or higher-order multiple pregnancies, we suggest avoiding routine cerclage (Grade 2C). (See "Triplet pregnancy", section on 'Unproven interventions' and "Twin pregnancy: Management of pregnancy complications", section on 'Overview' and "Twin pregnancy: Management of pregnancy complications", section on 'Patient selection for cerclage'.)
●Management of subsequent pregnancies – For patients with a successful history-indicated cerclage, we usually repeat history-indicated cervical cerclage in subsequent pregnancies. For those with a successful (delivery ≥34 weeks) ultrasound-indicated cerclage, we follow CL in subsequent pregnancies and repeat ultrasound-indicated cervical cerclage if CL is ≤25 mm before 24 weeks. If the previous ultrasound-indicated cerclage was unsuccessful (delivery <34 weeks), we perform history-indicated cerclage at 12 to 14 weeks of gestation in the subsequent pregnancy. We offer transabdominal or laparoscopic cervicoisthmic cerclage to patients who have failed to have a successful pregnancy outcome after a transvaginal history-indicated cerclage at 12 to 14 weeks of gestation. (See 'Management of future pregnancies following cerclage in index pregnancy' above.)
