Tommy's PregnancyHub

Cervical incompetence

When the cervix shortens and opens in the second trimester (16 to 24 weeks) or early in the third trimester without any other symptoms of labour it may be referred to as cervical incompetence or cervical insufficiency.

The cervix is the canal at the base of the womb (uterus) that connects it to the vagina. It is also known as the neck of the womb. When a pregnancy reaches full term the cervix begins to shorten (efface) and open (dilate), allowing the baby to be born. This is part of the normal labour and birth process.

When the cervix shortens and opens in the second trimester (16 to 24 weeks) or early in the third trimester without any other symptoms of labour it is sometimes referred to as "cervical incompetence" as this term is sometimes used incorrectly instead of “preterm birth”. True cervical incompetence, in which there is a structural problem with the cervix, is uncommon and most women who have a preterm birth will not have any problems in their following pregnancies, even without treatment.

What we discuss here is the cases in which there is a structural weakness in the cervix that caused preterm birth.

Structural cervical problems that are linked to premature birth

  • You may have undergone treatment for cervical cancer or precancerous cells such as trachelectomy (surgical removal of the cervix), LLETZ procedures or cone biopsy. In some cases, quite a lot of cervix may have been removed and it is a good idea to ask your gynaecologist whether more than 1 cm of tissue was removed.
  • You may have experienced previous obstetric cervical trauma, such as cervical tearing during labour or prior dilation and curettage (D&C). This involves opening the cervix and surgically removal of part of the lining of the uterus and/or contents of the uterus, for example carried out after a first trimester miscarriage or abortion.
  • You may have undergone a full or partially dilated emergency caesarean section in a previous pregnancy and had damage to the top of your cervix during the delivery of your baby.
  • You may have been born with a connective tissue disorder such as hypermobility or ehlers danlos syndrome, which effects the collagen within the tissues of the cervix causing it to be weak.
  • You may have been exposed to DES (Diethylstilbestrol) in the womb. DES was given to women up until 1971 as it was thought to prevent miscarriage but it has since been linked with issues of the reproductive system and preterm birth in those whose mother’s took it while pregnant.
  • You may have a uterine abnormality. Uterine abnormalities have not been shown to affect the structure of the cervix but they are linked to preterm birth.
  • You may have been born with a naturally weak or short cervix and this may be genetic .

If your cervix has been found to measure less than 25mm’s (2.5cm) during pregnancy it is a cause for concern and you should be treated as high risk for preterm birth. You may need treatment. You should also be monitored closely during future pregnancies.

Symptoms of cervical incompetence in pregnancy

There are no obvious symptoms you can look out for of the cervix opening too soon, whether this is due to cervical incompetence or other causes. Your cervix can shorten and dilate without any other signs.

If you have been told you are at risk of premature birth or you have any of the cervical problems listed above, it is important that you are monitored regularly in your pregnancy. This will include checks on the length of your cervix.

A pregnancy that has a risk of premature birth can be very scary. If at any time you are worried about any signs or symptoms you are experiencing; then you should contact your midwife immediately.

Look out for the symptoms below that could indicate premature labour.

  • an increase in pelvic pressure within the vagina or rectum.
  • an increase in discharge and/or a gush/repeat trickling of fluid, which could mean your waters have broken (preterm premature rupture of membranes).
  • bleeding or losing your mucus plug.
  • period type pains in your abdomen or lower back. These may have a rhythm or be constant.

Do I have cervical incompetence?

You are at higher risk of having cervical incompetence if you:

  • have previously had one or more premature births or miscarriages during the second or early third trimester
  • have any of the factors listed above.

A note on intrauterine infection and preterm birth

If you had an intrauterine infection (chorioamnionitis) in a previous premature birth, it is important to ensure your consultant considers the cervical problems listed above rather than assuming infection was the cause of the birth.

When a woman gives birth early the cervix shortens some time before birth. This allows bacteria (which are normally present in the vagina) to move up into the womb, which can develop into an infection.

Therefore it is very possible that it is the short cervix that allowed the infection to develop, rather than the infection causing the cervix to shorten and open.

Treatment for cervical incompetence

If your doctor thinks you are at risk of cervical incompetence or premature birth the length of your cervix will be monitored and if it is found to be short, treatment will be focused on prolonging your pregnancy.

You will have regular monitoring during your pregnancy with:

  • transvaginal scans (an ultrasound wand that is inserted into the vagina to give the best view of the cervix length)
  • vaginal swabs for markers of preterm birth (for example fetal fibronectin - a substance that is only present in the vagina when you are at increased risk of going into early labour)

This monitoring can be reassuring, or else can predict an increased chance of early delivery, before you are able to detect any symptoms yourself. It should start between 14-16 weeks of pregnancy.

Some consultants may also recommend antibiotic treatment to try and reduce the risk of infection, for example an antibiotic pessary that is inserted for one week of each month to try and prevent an infection happening. There is no evidence currently to support that this practice reduces the risk of early delivery.

If you are at very high risk of giving birth prematurely with cervical incompetence, the most common treatment is a stitch / cerclage, although the Arabin Pessary and vaginal progesterone are also recognised treatments for a short cervix.

Women without cervical incompetence but who have other risk factors for premature birth or whose cervix is shortening for other reasons may also benefit from the cervical stitch.

Read more about the cervical stitch and other treatments currently in use across the UK for cervical insufficiency and premature birth.

Research into cervical incompetence.

Our knowledge about cervical incompetence and the role it plays in premature birth is limited. For this reason, you may be asked to participate in research. It is your decision whether you wish to take part or not. Research into the causes and treatments for premature birth is very important to ensure that women receive the safest possible treatments with the best outcomes for both themselves and their babies and is a very important part of work done by Tommys.

Your feelings about cervical incompetence

Women have said to us that they suffer from feelings of guilt and self-hatred when they go through a late miscarriage or premature birth caused by cervical incompetent. This is very sad as the situation is not your fault, and usually there is nothing that you could have done to make a difference. It is important to seek professional help if you feel you are not coping and need support.

Some women do not like the term ‘incompetent cervix’, but it is used as a medical term. It does not describe you or your body.

Support groups for cervical incompetence

Support after loss and in subsequent pregnancies that are at risk of premature birth is very important. Being among those who understand all of your worries and concerns can be very comforting in your times of need. There are currently two support groups running on Facebook that are UK and Ireland based purely dedicated to cervical incompetence support. You can request to join if you need support.

Incompetent Cervix UK - a Facebook group for anyone and everyone in the UK and Ireland who would like advice, info or support on any aspect of cervical insufficiency.
UK TAC Support Group - a Facebook group specifically for women who have a transabdominal cerclage or are thinking of having one placed in the UK or in Ireland. It has been award nominated for the support it provides to its members.

Both groups send out joining messages to keep out trolls and selling pages, so please look out for a joining message from the admin team after you request to join.

Read more about the cervical stitch and other treatments currently in use across the UK for cervical insufficiency and premature birth.

  • NICE (2007) Laparoscopic cerclage for the prevention of recurrent pregnancy loss due to recurrent miscarriage, National Institute of Health and Clinical Excellence
  • J David, Steer P et al (2010) High risk pregnancy, management options, Elsevier Saunders
  • Warren JE1, Silver RM (2009) Genetics of the cervix in relation to preterm birth. Semin Perinatol. Oct;33(5):308-11. doi: 10.1053/j.semperi.2009.06.003
  • Personal communication, Professor Andrew Shennan, Professor of Obstetrics at King's College London
Review dates
Last reviewed: 12 June 2017
Next review: 12 June 2020