Most pregnancies are normal, healthy, and reach full term—but somewhere between nine and 10 percent of women deliver their babies early (before 37 weeks of pregnancy). In fact, preterm birth complications are the leading cause of death in children under age 5 worldwide, according to the World Health Organization.

For about 1 percent of expectant mothers who experience preterm labor, the cause is a condition called cervical insufficiency, formerly known as cervical incompetence. In cervical insufficiency, the cervix begins to dilate (widen) and efface (shorten and thin) during the second trimester.

While no woman wants to deal with a complication in pregnancy, the good news is that when cervical insufficiency is suspected (based on prior pregnancy history, or findings seen on ultrasound or physical exam), treatments are available. Cervical cerclage, a minor surgical procedure, is an effective and safe treatment option that can help prolong the pregnancy, ideally to full term. Another type of treatment involves supplementation with the hormone progesterone.

”Preterm birth is a common problem that we are constantly striving to address, and cervical cerclage is one of the ways we can prevent it,” says Katherine Kohari, MD, a high-risk pregnancy specialist with Yale Medicine.

In a normal pregnancy, a woman’s cervix (lower part of the uterus) will naturally begin to dilate when labor begins, as the body prepares for birth. Dilation is typically a direct response to contractions in the uterus. However, for some women, the opening and shortening begins gradually in the days and weeks before delivery.

Cervical insufficiency is the medical term for when these changes occur much earlier, around the fourth or fifth month of pregnancy, and in the absence of contractions. It can lead to very early delivery (before 24 to 28 weeks) or pregnancy loss. It is believed that cervical insufficiency is caused by a structural weakness of the cervix.

When the cervix opens prematurely, a woman’s risk for a preterm delivery greatly increases. Some women experience cervical insufficiency in one pregnancy but then go on to carry others full term. For others, though, the problem is recurrent. Once a woman has had a premature delivery, she has about a 30-percent risk of preterm birth in a future pregnancy.

Though the underlying causes of cervical insufficiency haven’t yet been pinned down, it’s thought that both genetic and environmental factors may play a role. Risk factors for the condition include the following: 

• Previous losses: Women who have miscarried in the second trimester two or more times appear to be at higher risk for cervical insufficiency.
• Collagen disorders: Genetic conditions affecting collagen (a protein in the body that gives skin and tissues strength and elasticity), such as Ehlers-Danlos syndrome or Marfan’s syndrome, can increase risk.
• Gynecologic history: Women with precancerous lesions of the cervix, who had them removed via a procedure called a cone biopsy (removing a cone-shaped piece of tissue from the cervix), or a LEEP (loop electrosurgical excision procedure), may be at higher risk of cervical insufficiency.

While many women have no advance warning for cervical insufficiency, some experience symptoms such as vaginal pressure, spotting or bleeding, nonspecific abdominal or lower back pain, or vaginal discharge. A pelvic exam may reveal that the cervix is soft, effaced, or dilated.

In women considered at risk, doctors may begin monitoring for the condition via a transvaginal ultrasound, beginning around week 16 of pregnancy. If signs of early cervical shortening are detected, the doctor may continue regular monitoring or may want to start treatment. For some women, a progesterone supplement may help stave off premature delivery. If the physician and patient are in agreement, her cervical insufficiency can be treated with a simple surgical procedure called cervical cerclage, which can help prolong the pregnancy.

Dr. Kohari notes that cervical cerclage is most often used for women with a history of at least one early loss in the absence of labor. “The classic example would be a patient who has suffered from a second-trimester pregnancy loss in which the pregnancy was uncomplicated, and all of a sudden she comes to the hospital because of vaginal pressure and delivers,” she says. “Somebody who, for whatever reason, has a slightly weaker cervix than the average person can benefit from sewing the cervix closed, giving a little extra support. It's been shown to help maintain a pregnancy longer.”

According to Dr. Kohari, cervical cerclage stitches the cervix closed, helping to keep the baby safely in the womb. The stitches remain in place until the pregnancy is near full term (about week 36 to 37) and are then removed. Though the baby could safely be delivered at this point, removing the stitches doesn’t necessarily trigger labor.

Cervical cerclage is an outpatient procedure, done in the hospital under regional anesthesia. There are two different types of cerclage techniques: 

• McDonald: A needle is used to place stitches through the cervix. The ends of the sutures are tied together to close it in a purse-string fashion.
• Shirodkar: This method involves dissecting around the cervix, placing the stitches around the cervix to keep it closed.

For complicated cases, including those in which the cervical cerclage hasn’t worked in the past, another technique called transabdominal cerclage is an option. This procedure involves making one or more incisions in the abdomen to reach the cervix, and then stitching it closed.

A cervical cerclage takes about an hour and patients go home later in the day. As with all surgeries, there is some risk of bleeding and infection. Though rare, there is also some risk of rupture to the amniotic sac, which can put a patient into labor. This is seen more commonly in patients who already have an open cervix at the time of cerclage.

Cervical cerclage is not used in women who are expecting twins, as it brings a higher risk for preterm birth.

Yale Medicine’s Maternal-Fetal Medicine specialists are skilled at diagnosing and treating cervical insufficiency. They have vast experience using both traditional types of cervical cerclage techniques, as well as with transabdominal cerclage.

Our researchers are also actively searching for answers to questions such as what prompts premature delivery and pregnancy loss.

“While cervical insufficiency can be worrisome for our patients, it is something we are experienced at dealing with, particularly when it comes to procedures like cervical cerclage,” Dr. Kohari says.