Insufficient Cervix
An insufficient cervix (formerly incompetent cervix) indicates a mechanical or tissue failure of the cervix to maintain the structural integrity/physical support necessary to sustain a pregnancy. An insufficient cervix can soften, ripen, and/or dilate too soon, often leading to preterm delivery.
The causes of an insufficient cervix are not known, but ultrasound can be used to monitor cervical length to determine a woman’s possible risk level for a weakened cervix as pregnancy progresses.
If a woman is determined to likely be at risk for insufficient cervix, a cerclage is usually recommended. A cerclage involves placing one or two sutures (stitches) in the cervix to structurally reinforce it to keep the cervix closed long enough for a fetus to mature and be delivered safely.
Women with a history of preterm labor or those at risk for insufficient cervix should have a risks and benefits discussion with their HCP regarding possible preventative measures.
Background
The cervix is the opening to the uterus that sits at the top of the inside of the vagina. It is the lower, cylindrical portion of the uterus that has small openings at each end and separates the uterus and vagina. These openings are blocked (mucus plug) during pregnancy, and then dilate during labor and delivery.
Insufficient (previously incompetent) cervix is usually defined as a “mechanical” or tissue failure of the cervix that leads to painless premature softening, shortening, and dilation – usually without contractions – that may result in preterm delivery or loss of a pregnancy.
The condition is estimated to occur in approximately 0.5% to 1% of pregnant women, but variations in its definition can skew this estimate. Given that preterm birth affects up to 10% of all deliveries, the actual prevalence of insufficient cervix could be higher.
Signs and Symptoms
There are usually no signs or symptoms of an insufficient cervix. The condition can either be found or suspected through a pre-scheduled ultrasound, or spotting and/or discomfort is present which leads to an exam. In serious cases, contractions can begin which could lead to preterm labor and delivery.
Women should call their HCP if they experience pelvic pressure, bleeding, backache, cramps, vaginal discharge, or spotting at any time during pregnancy.
Causes/Risk Factors
Specific factors that cause insufficient cervix are not known, and although there are some known risk factors, many women with an insufficient cervix do not have an identified risk factor.
Some factors that can increase risk are uterine defects or malformations, a short cervix, recent cervical/uterine surgery, a prior cerclage, carrying multiples, prior preterm delivery, previous trauma to the cervix, and family history.
It is not clear how uterine malformations lead to an insufficient cervix, but malformations are rather easily detected and, in most cases, can be corrected before a future pregnancy.
Diagnosis/Management
There is no single test before or during pregnancy that can be used to determine whether a cervix is able to retain a pregnancy.
If a pregnant woman has one or more risk factors, an HCP may do an ultrasound to assess the cervix early in pregnancy or prior to a pregnancy. Ultrasounds may be conducted more often to make sure there are no changes to the cervix too early. With a history of insufficient cervix or preterm birth, an HCP may perform an ultrasound every 2 weeks beginning around week 16 through week 24 or longer.
This may change to weekly ultrasound assessments if cervical length is 25 to 29 mm; a cerclage (see below) may be offered if cervical length is less than 25 mm.
Note: Transvaginal ultrasonography may be used as a predictor of preterm birth based on cervical length over time (by making sure it does not change) but cannot rule out other causes of preterm birth.
The actual diagnosis of insufficient cervix is difficult. If an insufficient cervix is suspected, an HCP may also conduct a pelvic exam to check if fetal membranes are protruding through a possibly dilated cervix, as well as check and monitor for contractions and test for infection.
If preterm labor occurs, an HCP will explain possible treatments and the risks and benefits of trying to stop or delay labor.
If labor has not begun, an HCP might suggest progesterone injections or suppositories, or a preventative cerclage. Further research is needed to determine the best use of progesterone in cervical insufficiency, but it is commonly used for the prevention of preterm labor.
Cerclage
A cerclage is a surgical procedure that can help prevent complications from an insufficient cervix (mainly preterm delivery). During this procedure, the cervix is reinforced and stitched closed with one or two strong sutures under regional anesthesia. The sutures are removed during the last month of pregnancy or sooner if labor begins or contractions start.
Although a cerclage may be recommended if cervical length is shorter than 25 mm, researchers do not know what the optimal cervical length is at specific times during pregnancy to successfully retain a pregnancy. Because of this, cervical cerclage may be used too often, and some “shorter” cervixes may in fact be strong enough to carry a pregnancy to term.
If a woman is less than 24 weeks pregnant, has a history of early premature birth, and ultrasound shows that the cervix is opening, a cerclage is recommended. A “rescue” cerclage on a thinning or dilating cervix is not recommended as this can risk tissue tearing and membrane puncture.
A preventative cerclage can also be used in women with a history of the cervix opening too early, even before the cervix opens in subsequent pregnancies. This may be done as early as the first trimester.
However, although cervical insufficiency does often recur in subsequent pregnancies, this history is not necessarily indicative of cervical length in the next pregnancy, and preventative cerclage may not be necessary. However, it remains common practice.
A cerclage is currently not recommended for women pregnant with multiples, even with a short cervix. The heavy uterine weight could force the cervix open with the cerclage, which could cause significant tissue trauma.
However, research is ongoing regarding the use of cerclage for multiples to prevent preterm labor. A study published in November 2020 of women with twin pregnancies and asymptomatic cervical dilation before 24 weeks found that a combination of cerclage, indomethacin (nonsteroidal anti-inflammatory drug) and antibiotics significantly decreased preterm birth at all evaluated gestational ages.
Additionally, a study published in May 2021 found that emergency cerclage in women (carrying twins) with cervical dilation and prolapsed membranes was associated with a overall 40% decrease in spontaneous preterm birth less than 28 weeks and a prolongation of latency by 5 weeks.
Action
Women should call their HCP if they experience pelvic pressure, backache, cramps, vaginal discharge, or spotting any time during pregnancy, or if they believe they may be in preterm labor.
Women with a history of preterm labor or those at risk for insufficient cervix should have a risks and benefits discussion with their HCP regarding possible preventative measures.
Women should also consider sharing and submitting their experience below regarding cervical insufficiency during pregnancy for other women who are currently going through the same experience.
Resources
Cerclage for the Management of Cervical Insufficiency (American College of Obstetricians and Gynecologists)
Cervical cerclage for the woman with prior adverse pregnancy outcome (Society for Maternal-Fetal Medicine)