Approximately 10% of pregnancies end in preterm delivery, defined as a delivery that occurs before week 37 of pregnancy (the average pregnancy lasts 40 weeks). Premature birth is a major cause of serious health problems in neonates (newborn babies), including respiratory distress, difficulty regulating body temperature, and infection. More than 85% of long-term disabilities in otherwise healthy babies and 75% of deaths among newborns occur as a result of preterm delivery.
A woman with an incompetent cervix is 3.3 times more likely to deliver prematurely. The cervix is the neck-shaped opening at the lower part of the uterus and is normally closed tight during pregnancy until the baby is ready to be delivered, at which point it expands (dilates) to roughly 4 in (10 cm) in diameter. An incompetent cervix is prone to dilating and/or effacing (shortening) prematurely during the second trimester. The growing fetus subsequently places too great a strain on the
A doctor might recommend a cerclage be performed if a woman has one or more of the following risk factors:
- a previous preterm delivery
- previous trauma or surgery to the cervix
- early rupture of membranes ("breaking water")
- hormonal influences
- abnormalities of the uterus or cervix
- exposure as a fetus to diethylstilbestrol (DES), a synthetic hormone that was used in the mid-twentieth century to treat recurrent miscarriages
Racial and socioeconomic factors influence a woman's risk of delivering prematurely: African-American women are at more risk (16–18%) than white women (7–9%); women under 18 and over 35 are also at greater risk. Less educated women are more likely to deliver prematurely. Smoking during pregnancy is associated with a 20–30% greater risk of delivering prematurely. Male fetuses are more likely to be born prematurely and have a higher rate of fetal death than female fetuses (a difference of 2.8–9.8%).
Elective cervical cerclage is a minor surgical procedure that is generally performed between 12 and 14 weeks of pregnancy (at the beginning of the second trimester) before symptoms of premature labor begin. Emergent cerclages are those placed later in pregnancy when cervical changes have already begun.
The patient will usually receive regional (epidural or spinal) anesthesia during the procedure, although general anesthesia is sometimes used. Spinal anesthesia involves inserting a needle into a region between the vertebrae of the lower back and injecting numbing medications. An epidural is similar to a spinal except that a catheter is inserted so that numbing medications may be administered as needed. Some women experience a drop in blood pressure when a regional anesthetic is administered; this effect can be countered with fluids and/or medications.
While there are numerous techniques for performing cerclage, the McDonald and Shirodkar techniques are the most common. The McDonald cerclage involves stitching the cervix with a 0.2 in (5 mm) band of suture. The cerclage is placed high on the cervix when the lower part has already started to efface. The stitch is usually removed around week 37 of pregnancy. The classic Shirodkar procedure involves a permanent "purse-string" stitch around the cervix; because it will not be removed, a cesarean section will be necessary to deliver the baby. Most Shirodkar cerclages are now performed with a modified technique that allows the sutures to be later removed.
Some less common methods of cerclage include:
- Hefner (or Wurm) cerclage (usually reserved for later in pregnancy when there is little cervix to work with)
- abdominal cerclage (a permanent stitch performed through an abdominal incision instead of the vagina; reserved for when a vaginal cerclage has failed or is not possible)
- Lash cerclage (a permanent stitch performed before pregnancy because of trauma to the cervix or an anatomical abnormality)
Diagnosis of an incompetent cervix is usually done by medical history and/or by examination (manually during a pelvic exam or using ultrasound technology). Some symptoms of an incompetent cervix used to decide if a cerclage is necessary are:
- cervical dilation
- shortening of the cervix
- funneling of 25% or more (when the internal opening of the cervix has begun to dilate but the external opening remains closed)
Women who are more than 1.5 in (4 cm) dilated, who have already experienced rupture of membranes, or whose fetus has died are ineligible for cerclage.
Before the procedure may be performed, there are a number of preparatory steps that must be taken. A complete medical history will be taken. A cervical exam will
After the cerclage has been placed, the patient will be observed for at least several hours (sometimes overnight) to ensure that she does not go into premature labor. The patient will then be allowed to return home, but will be instructed to remain in bed or avoid physical activity for two to three days. Follow-up appointments will usually take place so that her doctor can monitor the cervix and stitch and watch for signs of premature labor.
While cerclage is generally a safe procedure, there are a number of potential complications that may arise during or after surgery. These include:
- risks associated with regional or general anesthesia
- premature labor
- premature rupture of membranes
- infection of the cervix
- infection of the amniotic sac (chorioamnionitis)
- cervical rupture (may occur if the stitch is not removed before onset of labor)
- injury to the cervix or bladder
The success rate for cervical cerclage is approximately 80–90% for elective cerclages, and 40–60% for emergent cerclages. A cerclage is considered successful if labor and delivery is delayed to at least 37 weeks (full term).
Morbidity and mortality rates
Approximately 1–9% of women will experience premature labor after cerclage. The risk of chorioamnionitis is 1–7%, but increases to 30% if the cervix is dilated greater than 1.2 in (3 cm). The risks associated with premature delivery, however, are far greater. Babies born between 22 and 25 weeks of pregnancy are at significant risk of moderate to severe disabilities (46–56%) or death (approximately 10–30% survive at 22 weeks, increasing to 50% at 24 weeks, and 95% by 26 weeks).
Depending on her specific condition, a woman may have some alternative therapies available to her to avoid or delay premature labor. These include:
- Bed rest. At least 20% of pregnant women in the United States have at least one week of bed rest prescribed to them at some point of their pregnancy. The idea of bed rest is to avoid putting unnecessary pressure on the cervix.
- Tocolytics. These are drugs that are designed to stop or delay labor. Ritrodrine, terbutaline, and magnesium sulfate are some common tocolytics.
- Antibiotics. Some infections are associated with a high risk of preterm labor (e.g., upper genital tract infection). Antibiotics may be successful in preventing preterm labor from occurring by treating the infection.
Enkin, Murray, et al. A Guide to Effective Care in Pregnancy and Childbirth, 3rd ed. Oxford: Oxford University Press, 2000.
Goldenberg, Robert L. "The Management of Preterm Labor." Obstetrics & Gynecology 100, no. 5 (November 2002): 1020–37.
MacDonald, Hugh. "Perinatal Care at the Threshold of Viability." American Academy of Pediatrics 110, no. 5 (November 2002): 1024–7.
Matijevic, Ratko, Branka Olujic, Jasua Tumbri, and Asim Kurjak. "Cervical Incompetence: The Use of Selective and Emergency Cerclage." Journal of Perinatal Medicine 29 (2001): 31–5.
Weismiller, David G. "Preterm Labor." American Family Physician February 1, 1999: 593–604.
American Academy of Family Physicians. 8880 Ward Parkway, Kansas City, MO 64114. (816) 333-9700. <http://www.aafp.org>.
American Board of Obstetrics and Gynecology. 2915 Vine Street, Dallas, TX 75204. (214) 871-1619. <http://www.abog.org>.
American College of Obstetricians and Gynecologists. 409 12th St., SW, PO Box 96920, Washington, DC 20090-6920. <http://www.acog.org>.
Bernstein, Peter S. "Controversies in Obstetrics: Cervical Cerclage." Third World Congress on Controversies in Obstetrics, Gynecology, and Infertility. 2002 [cited March 1, 2003]. <http://www.medscape.com/viewprogram/1964>.
Pincock, Stephen. "Cervical Cerclage Associated with Good Pregnancy Outcome." Reuters Health. February 13, 2003 [cited March 1, 2003]. <http://www.medscape.com/viewarticle/449414>.
"Shortened Cervix in Second Trimester Possible Warning Sign for Premature Birth." National Institute of Child Health and Development. September 18, 2001 [cited March 1, 2003]. <http://www.nichd.nih.gov/new/releases/cervix.cfm>.
Starzyk, Kathryn A. and Carolyn M. Salafia. "A Perinatal Pathology View of Preterm Labor." Medscape Women's Health eJournal. 2000 [cited March 1, 2003]. <http://www.medscape.com/viewarticle/408936_1>.
Weiss, Robin Elise. "The Incompetent Cervix." [cited March 1, 2003.] <http://pregnancy.about.com/library/weekly/aa011298.htm>.
Stephanie Dionne Sherk
WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?
A cervical cerclage is generally performed in a hospital operating room by an obstetrician/gynecologist who specializes in the areas of women's general health, pregnancy, labor and childbirth, prenatal testing, and genetics. Anesthesia will be administered by an anesthesiologist.
QUESTIONS TO ASK THE DOCTOR
- How many cerclages do you perform each year?
- What is your rate of complications?
- Why is cerclage recommended for my particular condition?
- What are my options for anesthesia?
- After the cerclage is placed, do I have to alter my day-to-day routine?
- What alternatives to cerclage are available to me?