The cervix is the opening to the uterus (womb) that sits at the top of the vagina (birth canal). It opens, cervical length shortens and gets thinner and softer so your baby can pass through the birth canal during labor and birth. A short cervix means the length of your cervix (also called cervical length) is shorter than normal. You may find out that you have a short cervical length during an ultrasound that you get as part of your regular prenatal care.
As babies grow in the womb, the weight of the pregnancy increases and exerts more pressure onto the cervix (the womb’s opening to the birth canal). In some women, the cervix is unable to sustain the pressure and may open prematurely. This condition is called cervical Incompetence (also referred to as cervical insufficiency) and could lead to preterm delivery or miscarriage in the second trimester, possibly third trimester as well.
Cervical incompetence is rare and only occurs in about 1% of pregnancies. Often times, gynecologists don’t check for it routinely unless you are at high risk. However, it is one of the most common causes of miscarriages in the second trimester. Uterine abnormalities and genetic disorders affecting a fibrous type of protein that makes up your body’s connective tissues might cause an incompetent cervix.
There aren’t any tests that can be done before pregnancy to reliably predict an incompetent cervix. However, certain tests done before pregnancy, such as an MRI or an ultrasound, can help detect uterine abnormalities. Cervical abnormalities, either congenital or as a result of trauma, are a risk factor for structural cervical weakness and, in turn, recurrent cervical insufficiency or incompetence.
If you have an incompetent cervix, you may not have any signs or symptoms during early pregnancy. Some women have mild discomfort or spotting over the course of several days or weeks starting between 14 and 20 weeks of pregnancy.
Be on the lookout for:
- A sensation of pelvic pressure
- A new backache
- Mild abdominal cramps
- A change in vaginal discharge
- Light vaginal bleeding
Who is at Risk for Cervical Incompetence?
Women who have had previous trauma or surgery to the cervix are at increased risk.
Cervical surgeries can weaken the cervix. Pregnant women who have had miscarriages or difficult previous births may also be at high risk. Additionally, certain cervical or uterine anomalies make some women more prone to cervical weakness, as well as women who have been exposed to DES (Diethylstilbestrol).
Diagnosing Cervical Incompetence
An incompetent cervix can only be detected during pregnancy. Even then a diagnosis can be difficult, particularly during a first pregnancy.
Your health care provider will ask about any symptoms you’re having and review your medical history. Be sure to let your doctor know if you’ve had a pregnancy loss during the second trimester or if you had a procedure on your cervix.
Your doctor might diagnose an incompetent cervix if you have:
- A history of painless cervical dilation and second-trimester deliveries
- Advanced cervical dilation and effacement before week 24 of pregnancy without painful contractions, vaginal bleeding, water breaking (ruptured membranes) or infection
Tests and procedures to help diagnose an incompetent cervix during the second trimester include:
- Transvaginal ultrasound. Your doctor may use transvaginal ultrasound to evaluate the length of your cervix and to check if membranes are protruding through the cervix. During this type of ultrasound, a slender transducer is placed in your vagina to send out sound waves that generate images on a monitor.
- Pelvic exam. Your doctor will examine your cervix to see if the amniotic sac has begun to protrude through the opening (prolapsed fetal membranes). If the fetal membranes are in your cervical canal or vagina, this indicates cervical insufficiency. Your doctor will also check for contractions and, if necessary, monitor them.
- Lab tests. If fetal membranes are visible and an ultrasound shows signs of inflammation but you don’t have symptoms of an infection, your doctor might test a sample of amniotic fluid (amniocentesis) to diagnose or rule out an infection of the amniotic sac and fluid (chorioamnionitis).
There aren’t any tests that can be done before pregnancy to reliably predict an incompetent cervix. However, certain tests done before pregnancy, such as an MRI or an ultrasound, can help detect uterine abnormalities that might cause an incompetent cervix.
Cerclage as Treatment for Cervical Incompetence
An OB-GYN can place a cerclage to hold the cervix closed in the event of cervical incompetence. In many cases, this has been effective in the prevention of preterm birth.
As a management of cervical insufficiency, cerclage is a surgical procedure performed through the vaginal canal. The surgeon stitches the cervix to prevent early dilation.
The non-surgical approaches of managing cervical incompetence like limiting activity, bed rest, and pelvic rest have not proven effective and their use is discouraged.
There are a few different ways that a cerclage can be placed. All of them serve to tighten and strengthen the cervix to keep it closed until the pregnancy is brought to term. Cerclage procedures usually entail closing the cervix through the vagina with the aid of a speculum. Another approach involves performing the cerclage through an abdominal incision (transabdominal cerclage).
- We can place the stitches around the outside of the cervix.
- We can make a small incision in the cervix, and then thread a surgical tape through it to close it.
If we do not catch the cervical incompetence until later in the pregnancy, the amniotic sac may start to protrude through the cervix. We can address this problem in one of two ways:
- We introduce a catheter (narrow tube) into the cervix and then inflate a small balloon at the end of the catheter.
- We insert a catheter through the urethra to fill the bladder with liquid. The pressure from the bladder can then nudge the amniotic sac back through the cervix.
- Once the amniotic sac is back in place, we can stitch up the cervix.
The higher the stitch is placed within the cervix, the lower the risk of preterm delivery. The stitches must be taken out prior to the beginning of labor, which is usually done at 36 weeks. It will not cause labor to start. However, if you go into early labor without having the stitches removed, it is a medical emergency and they must be removed immediately. In some scenarios, the baby must be delivered via Cesarean section.
What are the Risks of Cervical Cerclage?
As with any surgery, there are some risks to performing a cervical cerclage. These risks are rare and your medical team will take every precaution to ensure a safe procedure.
Possible complications of cervical cerclage include uterine rupture, maternal hemorrhage, bladder rupture, cervical laceration, preterm labor and premature rupture of the membranes. The likelihood of these risks is very minimal.
Some risks include:
- Damage to the cervix
- Maternal hemorrhage
- Preterm labor
- Preterm premature rupture of membranes (PPROM) – this means that the amniotic sac ruptures
- Cervical stenosis (narrowing or hardening of the cervix)
- Tearing in the cervix or uterine tissue, if you go into labor with the stitches still in place
Medications for Cervical Incompetence
Vaginal progesterone is a hormone that helps prepare your body for pregnancy. It may help prevent premature birth only if you have a short cervix and you’re pregnant with just one baby. You insert it in your vagina every day starting before or up to 24 weeks of pregnancy, and you stop taking it just before 37 weeks.
Progesterone may be as effective as cervical cerclage to prevent preterm birth in women with a singleton gestation, previous spontaneous preterm birth, and a short cervix. Given as a shot or inserted into the vagina daily, can be used to reduce the risk of preterm birth in certain high-risk women.
Progesterone is a hormone that is known to be important in preventing contractions promoting premature delivery and in supporting a pregnancy to full term. However, there is mixed evidence on the use of progesterone supplements to prevent cervical shortening but it may be recommended by your health care provider as well as or instead of a cervical stitch. Progesterone is given as either daily pessaries or weekly injections.
If you have reason to believe you are at risk for cervical incompetence, it’s important that you talk to your gynecologist about your concern. It’s better to catch this issue early so that the necessary steps can be taken to reinforce your cervix. Early treatment with cerclage can significantly reduce your chances of preterm labor and miscarriage.
If you’ve had an incompetent cervix during one pregnancy, you’re at risk of premature birth or pregnancy loss in later pregnancies. If you’re considering getting pregnant again, talk with your health care provider to understand the risks and what you can do to promote a healthy pregnancy outcome.