Incompetent Cervix

1 What is Incompetent Cervix?

Incompetent cervix 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. It typically presents as acute, painless dilatation of the cervix, which can lead to a mid trimester pregnancy loss. In women with this history, the risk of recurrence in a subsequent pregnancy is less than 30%.

In a woman with cervical incompetence, dilation and effacement of the cervix may occur without pain or uterine contractions. In a normal pregnancy, dilation and effacement occurs in response to uterine contractions. Cervical incompetence occurs because of weakness of the cervix, which is made to open by the growing pressure in the uterus as pregnancy progresses. If the responses are not halted, rupture of the membranes and birth of a premature baby can result.

2 Symptoms

You may have no symptoms of incompetent cervix. Or you may have mild symptoms beginning between 14 and 20 weeks such as:

  • Pelvic pressure
  • Premenstrual-like cramping
  • Backache
  • Vaginal discharge that increases in volume or becomes wetter
  • Vaginal discharge that changes from clear, white, or light yellow to pink or tan
  • Spotting (light vaginal bleeding)

There is still no good way to screen for cervical insufficiency, but if you're at risk for this condition, your practitioner may order regular transvaginal ultrasounds beginning at 16 weeks to measure the length of your cervix and check for signs of early effacement (shortening).

This screening is usually done every two weeks until you're 23 weeks along. If your practitioner finds significant changes, such as a cervix shorter than 25 millimeters (mm), you're at a much higher risk for preterm birth and may benefit from treatment.

3 Causes

Incompetent cervix can be caused by one or more of the following conditions:

  • Previous surgery on the cervix
  • Damage during a difficult birth
  • Malformed cervix or uterus from a birth defect
  • Previous trauma to the cervix, such as a D&C(dilation and curettage) from a termination or a miscarriage
  • DES (Diethylstilbestrol) exposure

4 Making a Diagnosis

The diagnosis of incompetent cervix is based on classic historic factors or by a combination of historic factors and transvaginal ultrasound 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.
  • 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.

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.
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.

— 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 may be noted. 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.

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) .

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.

5 Treatment

Several treatment methods exist for managing an incompetent cervix.

The following approach to management applies to women with singleton pregnancies. Cerclage is not indicated in any twin or other multiple pregnancies.

Women with prior pregnancy losses or preterm births

Candidates for history-indicated cerclage

— For women with a history-based diagnosis of cervical insufficiency, a history-indicated transvaginal cerclage at 12 to 14 weeks is recommended.

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.

These women are treated with hydroxyprogesterone caproate weekly from 16 to 36 weeks of gestation. Although randomized trials support the benefit of history-indicated cerclage (25 percent reduction in deliveries <33 weeks) and the benefit of progesterone supplementation 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. For these women, hydroxyprogesterone caproate prophylaxis against preterm delivery is administered. Monitor cervical length with transvaginal ultrasound (TVU) and apply a cerclage if cervical length is ≤25 mm.

Cervical length screening is initiated at about 14 weeks, but screening may start as early as 12 weeks in women with early second-trimester losses, recurrent second-trimester losses, or a prior large cold-knife conization. In women with prior preterm birth at 28 to 36 weeks, screening is initiated 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 to overt preterm labor or membrane rupture symptoms by three to six weeks. TVU screening is usually discontinued at 24 weeks of gestation, as cerclage is rarely performed after this time.

Intramuscular hydroxyprogesterone caproate supplementation is continued until 36 weeks, whether or not a cerclage is placed.
Vaginal progesterone and cerclage are equally efficacious in the prevention of preterm birth. Women with prior preterm birth are treated with intramuscular hydroxyprogesterone caproate and then cerclage is performed if the cervical length becomes ≤25 mm.

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. A single TVU cervical length measurement at 18 to 24 weeks is made in women with no prior preterm birth but risk factors for cervical insufficiency, and those with a short cervix (≤20 mm) are treated 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. If the patient delivers preterm, subsequent pregnancies are managed as described above and may warrant an ultrasound-indicated cerclage if cervical length is ≤25 mm.

If she delivers at term, a single cervical length measurement at 18 to 24 weeks is again performed and vaginal progesterone is again given 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 (e.g., <5 mm) on TVU examination.

Physical examination-indicated cerclage is a reasonable option for these women, in the absence of overt infection, labor, ruptured membranes, or significant hemorrhage (e.g., 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.

Amniocentesis is performed 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""]. Cerclage is not performed if there is evidence of subclinical infection as these pregnancies are at increased risk of preterm delivery and other pregnancy complications. 

Prior successful outcome after cerclage

—TVU cervical length screening is suggested 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.

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.


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.

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.

Vaginal discharge is the major side effect of using a pessary.

Indomethacin — 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.

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, bed rest/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.

6 Prevention

To try to prevent incompetent cervix, speak with your obstetrician and gynecologist.

Although prediction of cervical weakness has evolved and become more precise with the use of transvaginal ultrasonography, fetal fibronectin assays and the use of molecular markers, preventative measures resulting in prolongation of pregnancy with improved neonatal and longer-term outcomes remain more elusive.

Nonetheless, preventative methods that are employed include the avoidance of predisposing factors where possible, ranging from the avoidance of surgical trauma to the cervix and smoking cessation. Whether reduction of physical activity and work, cessation of sexual activity and the prophylactic use of cervical cerclage, progesterone and antibiotics are beneficial, remains unclear.

A diagnosis of precancerous changes in the cervix is associated with an increased risk of preterm birth and the type of treatment confers a small additional risk: the use of diathermy is associated with an adjusted OR of 1.72, compared with 1.1 for women treated using laser ablation.

Additionally, in the case of surgical termination of pregnancy and surgical or medical management of early miscarriage, there may be some value to using prostaglandin analogues such as misoprostol with antiprogesterone priming with mifepristone to avoid excessive dilatation force, haemorrhage and resultant cervical trauma, which can weaken the cervix considerably.

Cervical cerclage

There are no established guidelines of indications for cervical cerclage and the decision is often made by a senior obstetrician with some degree of specialist knowledge.

In women with true cervical weakness, as evidenced by multiple midtrimester losses or early deliveries associated with risk factors such as extensive cervical trauma, current evidence regarding the decision to perform elective transvaginal cervical cerclage is conflicting.

Although there does seem to be an overall reduction in the rates of preterm birth in some studies, this does not necessarily translate into improved neonatal outcomes. Despite this, it is a widely accepted practice in these very high-risk women where the benefit of cerclage outweighs risk.

There is little evidence to support the use of cerclage in women with two or fewer previous midtrimester losses (or preterm births) as an isolated finding, although clinicians are frequently compelled to do so by their need to help.

Anecdotally, other forms of cerclage, involving mobilising the bladder (Shirodkar cerclage) or insertion via laparotomy (transabdominal cerclage) may improve outcome but there is little prospective evidence to support. Cervical length remains a good predictor even in these women.

Mersilene® (Ethicon Ltd., Livingston, UK) tape is often the suture material of choice in preventing the suture from tearing out. It is unknown whether other materials confer any risk/benefit. A loop with two knots is frequently left to facilitate removal of the purse string (McDonald) cerclage.

An alternative approach to elective cerclage is insertion once an insufficient cervix, defined by the presence of dynamic changes of shortening, funnelling, dilatation or prolapse of membranes, and is detected on transvaginal ultrasonography.

However, there is conflicting evidence regarding the benefit of ultrasound-indicated and rescue cerclage, possibly because of the poor selection of women likely to benefit. Further research is needed in this area. In women who have evidence of an evolving pathological process, it is also unclear at what cervical length to intervene.

Elevated inflammatory markers such as interleukin-8 (IL-8) may identify those women at risk but interventions in these women need to be trialled.


Recently, the use of progesterone, which is responsible for maintaining myometrial quiescence during pregnancy, has been advocated in the prevention of preterm birth in women at risk.

The evidence on the correct dosage, agent, gestational age at initiation and cessation of intervention and the long-term maternal and neonatal adverse effects is, however, limited. Some clinicians use it in conjunction with cervical cerclage in high-risk women, although it remains unclear whether this confers benefit in terms of both prolongation of pregnancy and neonatal outcome.

Recent trials have targeted progesterone for the short cervix and the results are promising, suggesting a reduction by almost half in preterm births <34 weeks in singleton pregnancies.


As infection is likely to be the final event that precipitates preterm birth, it is reasonable to presume that treating organisms detected on vaginal swabs will prevent the stimulation of a complex inflammatory response with the concomitant release of cytokines.

The presence of abnormal vaginal flora and bacterial vaginosis in early pregnancy increases the risk of miscarriage and preterm birth but there is conflicting evidence regarding treatment.

Although early preterm birth is likely to have an infectious component, the use of ineffective antibiotics in inappropriate women at incorrect gestations can contribute to the controversy regarding their use.

7 Lifestyle and Coping

Lifestyle modifications are necessary in order to cope with incompetent cervix.

Know if you are at risk. Women who have previously had miscarriages in the second trimester are the most likely to have a cervical insufficiency. Disclose any prior pregnancy complications or miscarriages to your doctor.

This is particularly important if you have experienced a previous loss in the second trimester. Unfortunately, some women are not diagnosed with an incompetent cervix until they have suffered one or more late miscarriages.

Knowing about this condition in advance will allow your doctor to monitor your condition more closely from the beginning. This can result in earlier detection of a weak cervix, which leads to an increased chance of prolonging the delivery. Any surgery on the cervix also puts women at risk, including surgery following an abnormal pap smear.

Be attentive to possible symptoms. Although it is possible for an incompetent cervix to be present without any outward symptoms, in some cases there may be warning signs. These would typically occur between 14 and 22 weeks of pregnancy and include backache, discharge or warm liquid felt within the vagina, pelvic pressure, pain when urinating or sensation of a lump in the vagina.

Contact your OB/GYN immediately if you notice any of these symptoms. Although they may be completely unrelated to an incompetent cervix, it is always best to err on the side of caution and let the doctor do a complete exam to rule it out. This might include an ultrasound.

Keep in mind that most diagnoses of cervical insufficiency are based on a woman’s past medical history of miscarriage during the second trimester. If you do have a cervical insufficiency, you have some medical options.

Discuss treatment options with your doctor. He or she will be able to lay out the possible options -- cerclage, a pessary, and progesterone -- and tell you which ones would be available to you. Keep in mind that a cerclage (suturing the cervix closed) is by far the most common treatment, and allows many women with previous histories of miscarriage to successfully carry a baby to term.

A pessary, similar to the outer ring of a diaphragm, changes the angle of the cervix and reinforces it. Finally, progesterone treatments would be a weekly treatment of shots of hormone progesterone called hydroxyprogesterone caproate.

Consider with your doctor whether serial ultrasounds might be a good first step. With ultrasounds every two weeks during the second trimester of your pregnancy, the doctor can monitor the risk of an incompetent cervix. If he or she sees warning signs, then you can have a cerclage or a course of progesterone treatment.

Ensure you are getting adequate rest. It may be necessary for your doctor to recommend that you go on bed rest for a while, or even for the remainder of your pregnancy.

If this is suggested to you, do not take it lightly. Bed rest is exactly what it sounds like: you rest in bed with your feet up and do nothing strenuous. Lying in bed can help reposition the baby so as to alleviate pressure on the cervix.

Ask your doctor about vigorous exercise. He or she might suggest you refrain from high-intensity workouts and from having sex. Because your cervix is weak, exercise can further exacerbate your condition.

Do your kegels. Kegel exercises strengthen your pelvic floor muscles. To ensure that you are doing them correctly, while you are urinating clench your muscles to stop the flow of urine, and then release to continue the flow; that is what exercising your kegels feels like.

While is it not certain that kegels will prevent an incompetent cervix, they do have certain benefits including enhanced sexual pleasure, aiding in vaginal birth, help for incontinence and a quicker postpartum recovery.

8 Risks and Complications

There are several complications associated with incompetent cervix, which include:


A miscarriage is the loss of a pregnancy during the first 20 weeks of gestation. The American Pregnancy Association states that about one in four miscarriages are caused by an incompetent cervix. The symptoms of a miscarriage include:

  • abnormal vaginal bleeding
  • cramping
  • backache
  • disappearance of pregnancy symptoms
  • a change in vaginal discharge

Most women will be able to pass the tissue without the need for intervention. Some women may need medication or a small surgical procedure to help remove the tissue.

Premature Birth and Stillbirth

A “preterm” labor or a premature birth occurs when the baby is born too early — after 20 weeks but before the 37th week of pregnancy. A baby puts a lot of pressure on the cervix as it grows. If the cervix is not able to withstand the pressure, the membranes may rupture. If this happens, that mother may go into labor.

A baby born too early has an increased risk of disease, developmental delay, mental retardation, and death. The loss of pregnancy after the 20th week of gestation is called a stillbirth.

A fetus born before 23 weeks cannot survive outside of the mother's womb. Unfortunately, the majority of premature births in woman with an incompetent cervix occur between the 18th and 22nd week of gestation.