The cervix is the narrow lower end of the uterus that goes into the vagina.

• In a normal pregnancy, the cervix stays firm, long, and closed until late in the 3rd trimester.
• In the 3rd trimester, the cervix starts to soften, get shorter, and open up (dilate) as a woman's body prepares for labor.

An insufficient cervix may begin to dilate too early in pregnancy. If there is an insufficient cervix, the following problems are more likely to occur:

• Miscarriage in the 2nd trimester
• Labor begins too early, before 37 weeks
• Bag of water breaks before 37 weeks
• A premature (early) delivery

No one knows for sure what causes an insufficient cervix, but these things may increase a woman's risk:

• Being pregnant with more than 1 baby (twins, triplets, or more)
• Having an insufficient cervix in an earlier pregnancy
• Having a torn cervix from an earlier birth
• Having previous miscarriages by the 4th month
• Having previous first or second semester abortions
• Having a cervix that did not develop normally
• Having a cone biopsy or loop electrosurgical excision procedure (LEEP) on the cervix in the past due to an abnormal Pap smear

Often, you will not have any signs or symptoms of an insufficient cervix unless you have a problem it might cause. That is how many women first find out about it.

If you have any of the risk factors for insufficient cervix:

• Your health care provider may do an ultrasound to measure the length of your cervix when you are planning a pregnancy, or early in your pregnancy.
• You may have physical exams and ultrasounds more often during your pregnancy.

An insufficient cervix may cause these symptoms in the 2nd trimester:

• Abnormal spotting or bleeding
• Increasing pressure or cramps in the lower abdomen and pelvis

If there is a threat of premature birth, your provider may suggest bed rest. However, this has not been proven to prevent loss of pregnancy, and may result in complications for the mother.

Depending on the length of the cervix, your provider may suggest you have a cerclage. This is a surgery to treat an insufficient cervix. During a cerclage:

• Your cervix will be stitched closed with a strong thread that will remain in place during the whole pregnancy.
• Your stitches will be removed near the end of the pregnancy, or sooner if labor begins early.

Cerclages work well for many women.

Sometimes, medicines such as progesterone are prescribed instead of a cerclage. These help in some cases to prevent preterm birth.

Incompetent cervix; Weak cervix; Pregnancy - insufficient cervix; Premature labor - insufficient cervix; Preterm labor - insufficient cervix

Berghella V, Ludmir J, Owen J. Cervical insufficiency. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Philadelphia, PA: Elsevier; 2021:chap 35.

Buhimschi CS, Mesiano S, Muglia LJ. Pathogenesis of spontaneous preterm birth. In: Lockwood CJ, Copel JA, Dugoff L, et al, eds. Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice. 9th ed. Philadelphia, PA: Elsevier; 2023:chap 7.

Turocy J, Williams Z. Early and recurrent pregnancy loss: etiology, diagnosis, treatment. In: Gershenson DM, Lentz GM, Valea FA, Lobo RA, eds. Comprehensive Gynecology. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 16.

Updated by: LaQuita Martinez, MD, Department of Obstetrics and Gynecology, Emory Johns Creek Hospital, Alpharetta, GA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.