Cervical Insufficiency and Miscarriage Risk

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One of the few recognized causes of a late-term pregnancy loss is a condition known as cervical insufficiency, also referred to as an incompetent cervix. The condition is characterized by the premature dilation and thinning of the cervix before a pregnancy has reached full-term.​

The cervix is defined as the lower third portion of the uterus, which opens up into the vagina. It is mostly made up of muscle tissue and serves to allow the passage of a fetus from the uterus through the vagina during birth. When cervical incompetence occurs, a woman may experience preterm birth or pregnancy loss as the cervix is simply too weak to bear the growing pressure from within the uterus.

Cervical insufficiency is typically caused by irregularities in the cervix or uterus. According to the American Pregnancy Association, an incompetent cervix occurs in about one in every 100 pregnancies. These irregularities may be congenital (present at the time of birth) or the result of trauma to the cervix (including surgical procedures like cone biopsies).

While around 80% of all pregnancy losses occur during the first trimester, a small fraction of women will suffer loss in the second or third trimester. Of these late-term events, as many as one in four will be the result of an incompetent cervix.

Medical interventions may help if the problem is caught early enough.


An incompetent cervix can be challenging to diagnose because it is often entirely asymptomatic (meaning without symptoms). It can often occur without pain or contractions typically seen in other types of miscarriage or preterm events.

If symptoms are present, they tend to be mild and may include:

  • Pelvic pressure
  • Cramping
  • Backache
  • Changes in the volume, color, or consistency of vaginal discharge
  • Mild contractions

Cervical insufficiency occurs after 14 weeks of gestation and is not considered a factor in first-trimester miscarriages.


Cervical insufficiency can only be diagnosed during pregnancy and even then, it is difficult to confirm. In most cases, it can only be diagnosed when there is physical evidence of dilation occurring without painful contractions, vaginal bleeding, ruptured membranes (water breaking), or infection.

Cervical insufficiency is most often investigated in women who have had either a history of it or a history of short labors and progressively earlier deliveries. If cervical insufficiency is suspected, the doctor may carry out a number of evaluative tests, including:

  • Pelvic exam to see if there are fetal tissues are protruding into the cervical canal
  • Transvaginal ultrasound, inserted gently into the vagina, to determine the length of the cervix and the extent of any dilation
  • Amniocentesis (the removal of a sample of amniotic fluid) to rule out infection

While there are not any tests that can be used before pregnancy to predict an incompetent cervix, there are some able to detect uterine abnormalities consistent with the condition. These evaluations are most often pursued in women who have had repeated miscarriages or a history of preterm births.


When faced with cervical insufficiency, treatment practices can vary significantly from one doctor to the next. This is due to the fact that no single procedure has been shown to be more or less effective in preventing preterm birth than others. As such, options may include:

  • Close monitoring with no treatment unless the pregnancy appears threatened
  • Cervical cerclage, the insert of a stitch or suture to help reinforce the cervix
  • Cervical pessary, an intravaginal medical device used to support the cervix
  • Progesterone supplements to help prevent early delivery

A Word From Verywell

While an incompetent cervix, unfortunately, cannot be diagnosed until you're already pregnant and experiencing symptoms, you can keep a close watch for any of the symptoms discussed here and make sure to bring up any concerns with your doctor. With close monitoring and possibly a treatment plan, you and your doctor can make your best effort to prevent preterm birth.

6 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. ACOG Practice Bulletin No.142: Cerclage for the management of cervical insufficiency. Obstet Gynecol. 2014;123(2 Pt 1):372-9. doi:10.1097/01.AOG.0000443276.68274.cc

  2. Vink J, Feltovich H. Cervical etiology of spontaneous preterm birthSemin Fetal Neonatal Med. 2016;21(2):106–112. doi:10.1016/j.siny.2015.12.009

  3. American Pregnancy Association. Incompetent Cervix: Weakened Cervix.

  4. ACOG Practice Bulletin No. 200 Summary: Early Pregnancy Loss. Obstet Gynecol. 2018;132(5):1311-1313. doi: 10.1097/AOG.0000000000002900

  5. Nott JP, Bonney EA, Pickering JD, Simpson NA. The structure and function of the cervix during pregnancyTranslational Research in Anatomy. 2016;2:1-7. doi:10.1016/j.tria.2016.02.001

  6. Mönckeberg M, Valdés R, Kusanovic JP, et al. Patients with acute cervical insufficiency without intra-amniotic infection/inflammation treated with cerclage have a good prognosisJ Perinat Med. 2019;47(5):500–509. doi:10.1515/jpm-2018-0388

By Krissi Danielsson
Krissi Danielsson, MD is a doctor of family medicine and an advocate for those who have experienced miscarriage.