ConditionWomen's & pregnancy health
Cervical Incompetence (Incompetent Cervix)
Cervical incompetence, now usually called cervical insufficiency, is a weakness of the cervix that causes it to shorten and open painlessly during pregnancy, usually in the second trimester, without contractions or labor. It can lead to miscarriage or very early preterm birth. Risk factors include previous cervical surgery, a past second-trimester loss and uterine abnormalities. In high-risk pregnancies, it can be found early with cervical length ultrasound and treated with a stitch (cerclage) or vaginal progesterone.
Also called: Cervical insufficiency, incompetent cervix, weak cervix
At a glance
- What it is
- A cervix that opens too early in pregnancy without contractions.
- When it happens
- Usually between about 14 and 27 weeks.
- Warning signs
- Pelvic pressure, mild cramps or backache, increased discharge, light bleeding, often nothing at all.
- Diagnosis
- History of painless second-trimester loss, or a short cervix on transvaginal ultrasound.
- Treatment
- Cervical cerclage (stitch), vaginal progesterone, and close monitoring.
When to get help
Call 911 or go to the ER
- Fluid gushing or leaking from the vagina before 37 weeks
- Feeling something bulging in the vagina, or seeing membranes
- Heavy bleeding, or regular painful contractions before 37 weeks
See a doctor within a day or two
- New pelvic pressure, a dull backache, or menstrual-like cramps in the second trimester
- A change in vaginal discharge to watery, mucus-like or bloody
- Fever above 38 °C (100.4 °F) or foul-smelling discharge with a cerclage in place
Book a routine appointment
- Before or early in pregnancy if you have had a second-trimester loss, preterm birth, or cervical surgery such as a cone biopsy or LEEP
What happens in cervical insufficiency
The cervix is the lower part of the uterus. In pregnancy it normally stays long, firm and closed until labor, holding the pregnancy in. In cervical insufficiency, the cervix softens, shortens and dilates in the second trimester without the painful contractions of labor. As it opens, the amniotic sac can bulge into the vagina, rupture early, or become infected (chorioamnionitis), leading to miscarriage or extremely early birth.
The term "incompetent cervix" is still used, but many people find it hurtful, so doctors now prefer cervical insufficiency. See also cervical insufficiency.
Symptoms
Cervical insufficiency is often silent. When symptoms occur, they are usually mild and easy to mistake for normal pregnancy changes:
- a feeling of pressure in the pelvis or vagina
- a new, dull lower backache
- mild cramps like period pain
- increased vaginal discharge, which may become watery, mucus-like or tinged with blood
- light spotting or bleeding
Causes and risk factors
- Previous cervical surgery: cone biopsy, LEEP (loop excision) for abnormal cervical cells, especially deeper or repeated procedures
- Cervical injury during a previous delivery, a dilation and evacuation, or a difficult cesarean at full dilation
- A previous second-trimester loss or very preterm birth with painless dilation
- Uterine abnormalities, such as a septate or bicornuate uterus
- Connective tissue disorders, such as Ehlers-Danlos syndrome
- In utero exposure to DES (diethylstilbestrol), now rare
- Inflammation or infection in the uterus, which can weaken the cervix
Often no specific cause is found.
Diagnosis
There is no single test. Cervical insufficiency is diagnosed by:
- History: one or more second-trimester losses with painless cervical dilation, without labor or bleeding from the placenta.
- Transvaginal ultrasound: measures cervical length. A cervical length under 25 mm before 24 weeks is considered short and raises the risk of preterm labor and birth.
- Physical exam: a dilated cervix found on examination in the second trimester.
People at higher risk, such as those with a previous preterm birth, usually have serial cervical length scans from about 16 weeks. Many practices also measure cervical length at the routine anatomy scan.
Treatment
Cervical cerclage
A cerclage is a strong stitch placed around the cervix to help keep it closed. It is usually done through the vagina under regional or general anesthesia. Types:
| Type | When | Who it is for |
|---|---|---|
| History-indicated | At 12 to 14 weeks | One or more prior second-trimester losses from painless dilation, or a previous cerclage for this reason |
| Ultrasound-indicated | Before 24 weeks | A previous spontaneous preterm birth before 34 weeks and a cervical length under 25 mm |
| Physical exam-indicated (rescue) | Second trimester | A dilated cervix found on exam, without labor or infection |
| Transabdominal | Before or early in pregnancy | When a vaginal cerclage has failed or is not possible |
The stitch is usually removed at about 36 to 37 weeks, or earlier if labor starts or the waters break. Risks include infection, bleeding, ruptured membranes and cervical tearing if labor begins with the stitch in place.
Vaginal progesterone
For people with a short cervix (20 mm or less) found on ultrasound and no previous preterm birth, nightly vaginal progesterone reduces the risk of preterm birth. Progesterone is also used in some people with a previous preterm birth.
Other measures
- Cervical pessary: a silicone ring around the cervix. Study results are mixed, and it is used selectively.
- Activity: strict bed rest is not recommended, because it does not prevent preterm birth and raises the risk of blood clots. Your doctor may advise avoiding heavy lifting or sex in some cases.
- Steroid injections to mature the baby's lungs if preterm birth seems likely, and magnesium sulfate for brain protection before 32 weeks.
Outlook
With early identification and treatment, many people with cervical insufficiency go on to deliver at or near term. Having had cervical insufficiency once raises the risk in later pregnancies, so planning with an obstetrician or maternal-fetal medicine specialist before or early in the next pregnancy is important.
Frequently asked questions
What are the signs of an incompetent cervix?
Often there are no signs. Some people notice pelvic pressure, a dull backache, mild cramps, increased or watery discharge, or light spotting in the second trimester. Because these are subtle, high-risk pregnancies are monitored with cervical length ultrasounds.
What causes cervical incompetence?
Common causes include previous cervical surgery such as cone biopsy or LEEP, injury to the cervix in an earlier delivery or procedure, uterine abnormalities, and connective tissue disorders. Often no clear cause is found.
How is cervical insufficiency treated?
The main treatments are a cervical cerclage (a stitch around the cervix) and vaginal progesterone for a short cervix. Which one is used depends on your history and the cervical length on ultrasound.
Can you carry a baby to term with an incompetent cervix?
Yes. Many people with cervical insufficiency reach term or near term with a cerclage, progesterone and close monitoring. Early planning in the next pregnancy gives the best chance of a full-term birth.
Is bed rest recommended for a short cervix?
No. Research shows bed rest does not prevent preterm birth and increases the risk of blood clots and muscle loss. Your doctor may suggest limiting heavy lifting or intercourse, but normal daily activity is usually encouraged.
Sources
This guide was written from current patient and clinical guidance, including:
- American College of Obstetricians and Gynecologists (ACOG): Practice bulletin, cerclage for the management of cervical insufficiency
- Society for Maternal-Fetal Medicine: Guidance on progesterone and preterm birth prevention
- NHS: Cervical stitch (cerclage)
- MedlinePlus (US National Library of Medicine): Incompetent cervix
- Royal College of Obstetricians and Gynaecologists: Cervical cerclage guideline