Incompetent Cervix and Pregnancy

An incompetent cervix is one that undergoes abnormal widening during pregnancy. In a normal pregnancy, the cervix remains tightly closed until the pregnancy comes to term, at which point the cervix widens due to uterine contractions. An incompetent cervix thins and widens prematurely, usually between the third and thirteenth week of pregnancy.

Without treatment, an incompetent cervix can result in miscarriages or premature delivery and an increased risk of infection. The condition can be treated with bed rest, medication and cervical cerclage surgery. Incompetent cervix accounts for up to 25 percent of all second trimester miscarriages.

Causes and Risks of Incompetent Cervix

A number of risk factors can cause an incompetent cervix. Cervical cancer biopsies often contribute to an incompetent cervix. Cervical cancer "cone biopsies" are used as a cervical cancer screening tool. Treatment of cervical cancer can cause cervical trauma, damaging the cervix and making an incompetent cervix more likely.

In addition to cervical cancer, any form of cervical trauma or surgery increases the risk of an incompetent cervix during pregnancy. Artificial cervical dilation during an abortion can sometimes damage the cervix.

Other factors that contribute to an incompetent cervix include a history of miscarriages in previous pregnancies, physical cervical abnormalities and cervical birth defects. Women whose mothers took diethylstilbestrol (DES) during pregnancy have an increased risk of an incompetent cervix and miscarriage. DES was prescribed to prevent miscarriage, but was found to cause cervical defects.

In some cases, a pregnancy ends with miscarriage due to a spontaneous incompetent cervix, and no reason for the condition can be found. A future pregnancy has a high chance of developing an incompetent cervix without precautionary treatment to prevent cervical widening.

Diagnosing Incompetent Cervix

An incompetent cervix can be treated if diagnosed early enough. The cervical widening is usually painless. Regular prenatal checkups can detect cervical widening.

An incompetent cervix may cause vaginal spotting and bleeding. Any spotting during pregnancy should be reported to your doctor, no matter what the underlying cause. If not detected soon enough, cervical widening eventually causes premature amniotic membrane rupture (when the "waters" break), starting labor and usually resulting in fetal death.

Incompetent Cervix Treatment: Cerclage

Once an incompetent cervix is diagnosed, treatment may prevent a premature end to the pregnancy. The later in pregnancy an incompetent cervix develops, the better the chances of a successful pregnancy.

Medication may be advised to relax the uterus and prevent premature labor. However, the most successful treatment for an incompetent cervix is a surgical technique known as cervical cerclage.

Cervical cerclage stitches the cervix shut, preventing further cervical widening and lowering the chance of miscarriage. The cerclage stitches stay in place until the pregnancy comes to term, at which point the cerclage stitches are removed.

Cervical cerclage is most often recommended between the fourteenth and sixteenth weeks of pregnancy. After cervical cerclage, bed rest is recommended for a full 24 hours. After this point, exercise should be limited for the remainder of the pregnancy. Plenty of rest is recommended, and sexual intercourse should be avoided until the end of the pregnancy.

Cervical cerclage has a high success rate: between eighty to ninety percent of women who undergo the procedure deliver healthy babies. Cerclage works best when performed early in pregnancy, so prompt diagnosis of an incompetent cervix is essential. Consult your doctor about cervical cerclage if you have a history of incompetent cervix.

Resources

Beers, M. H., & Berkow, R., eds. (1999). Normal pregnancy, labor, and delivery. The Merck Manual of Diagnosis and Therapy, 17th Edition. NJ: Merck Research Laboratories.

Callahan, T. L., Caughey, A. B., & Heffner, L. J. (2001). Blueprints in Obstetrics and Gynecology, 2nd Edition. MA: Blackwell Publishing.

HealthAtoZ. (nd). Incompetent cervix.

Hendrickson, G. (updated 2001). Incompetent cervix.