Weak cervix (cervical incompetence or cervical insufficiency)

A weak cervix is when the cervix shortens and opens in the second or early in the third trimester, without any other symptoms of labour.

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 and will open (dilate) with contractions, allowing the baby to be born. This is part of the normal labour and birth process.

A weak cervix is when there is a structural problem with the cervix. If you have a weak cervix, it can shorten and open in the second or early in the third trimester, without any symptoms of labour. This can sometimes lead to a late miscarriage or premature labour. This is uncommon.

A weak cervix is sometimes known as cervical incompetence or cervical insufficiency. These terms do not sound pleasant but try to remember they are medical terms. It does not describe you or your body. 

“I lost my first baby at 20 weeks due to an ‘incompetent cervix’. Nobody could have predicted this would happen, but I still blamed myself for ‘losing’ my baby. We need to understand that this is a medical condition. Nobody is to blame. Getting a diagnosis is vital, so that you can then get the right treatment to support you through any future pregnancies.”


Symptoms of a weak cervix in pregnancy

Unfortunately, there are often no obvious symptoms of the cervix opening early. Your cervix can shorten and open without any other signs. 

Sometimes some discharge can come from the exposed membranes. Call your midwife or maternity unit if you have any discharge during your pregnancy that you are worried about. 

A weak cervix is usually diagnosed after 1 or more late miscarriage or premature labour and after other causes have been excluded. 

Symptoms of premature labour

The cervix opening early can cause premature labour, so it’s important to know the signs, including: 

  • regular contractions or tightenings
  • an increase in discharge – this can be due to membranes coming through the neck of the womb, or your waters breaking early (preterm premature rupture of membranes
  • period-like pains in your abdomen or lower back – these may have a rhythm or be constant
  • backache that’s not usual for you.  

Call your midwife or hospital maternity unit straight away if you think you are in early labour. It may be a false alarm, but it’s best to get checked out. Find out more about the symptoms of premature labour.

Am I at risk of a weak cervix?

You are at higher risk of having a weak cervix if you have had one or more premature births or miscarriages that happened during the second or early third trimester (generally at 34 weeks or earlier).  

Other risk factors for a weak cervix include:

Surgical treatment 

You may have received treatment for cervical cancer or precancerous cells. These treatments include trachelectomy (surgical removal of the cervix), LLETZ procedures or cone biopsy. In some of these procedures, a significant amount of cervix may have been removed. Your healthcare professional may need to monitor your cervix during pregnancy if more than 1cm of tissue is removed. 

Cervical trauma

This may include cervical tearing during labour or dilation and curettage (D&C). D&C involves opening the cervix and removing part of the lining or inside of the uterus, after an early miscarriage or abortion (termination). 

Previous emergency c-section

If you previously had a full or partially dilated emergency caesarean section (a section in the second stage of labour), there may be damage to the top of your cervix during the birth.  

Connective tissue disorders 

You may have been born with a connective tissue disorder such as hypermobility or ehlers danlos syndrome. This effects the collagen within the tissues of the cervix causing it to weaken.  

Exposure to Diethylstilbestrol (DES) medication

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. It has since been linked with issues of the reproductive system and premature birth in those whose mothers took it during pregnancy. 

Uterine abnormality

Uterine (womb) abnormalities have not been shown to affect the structure of the cervix, but they are associated with premature birth.


You may have been born with a naturally weak or short cervix and this may be genetic.

Treatment for a weak cervix

Your doctor may offer you treatment to try and stop your baby being born too early. 

You may be offered to have the length of your cervix monitored. If your cervix measures less than 25mm (2.5cm), you are considered to have a high risk for premature labour. You will be monitored closely and given treatment to help you and your baby reach full term. 

Monitoring should start by 16 weeks of pregnancy, and will include the following:

  • Transvaginal scans – where an ultrasound wand is inserted into the vagina to give the best view of the cervix length.
  • Vaginal swabs for signs of premature labour – for example fetal fibronectin, which is a substance that is only present in the vagina when you are at increased risk of early labour. 

Some consultants may check for unusual bacteria or infections in the vagina and offer treatment. 


You may be offered progesterone. This is a hormone that can help prevent contractions and help a pregnancy continue to full term. This will be given to you as a small tablet that you put into your vagina or anus.  

Having a cervical stitch

If you are at very high-risk of premature labour and have a weak cervix, the most common treatment is a cervical stitch or cerclage. A cervical stitch is an operation where a stitch is placed around the cervix (neck of the womb). This may help to keep the cervix closed and reduce the risk of premature birth. 

There is no definite evidence to show that a cervical stitch will prevent you going into labour early if you are pregnant with more than 1 baby. Find out more about pregnancy with multiple babies

Your consultant will advise you if you should rest in hospital or at home. They’ll also talk to you about what level of activity is appropriate for you, to reduce the risk of preterm birth. 

Read more about treatments to prevent a premature birth

Coping with having a weak cervix

Some people have told us that they feel guilty when they go through a late miscarriage or premature birth caused by cervical incompetence. 

This is the why some people prefer to use the terms weak cervix or early cervical dilation, because the word ‘incompetence’ feels like it is assigning blame. 

Having a weak cervix is not your fault. But if you have had a traumatic experience, this can sometimes lead to negative thoughts.

If you are finding it difficult to cope with your feelings and emotions, you may need some treatment or counselling. 

Talk to your GP about how you are feeling. They will help you find the right treatment and support.

You can also talk to a Tommy’s midwife free of charge from 9am–5pm, Monday to Friday on 0800 0147 800 or you can email them at [email protected]

Research into having a weak cervix

We still don't fully understand cervical incompetence and the role it plays in premature birth. Research is vital so that we can identify which women are likely to go into labour early, and help them carry their baby for as long as possible.

Find out more about our current research projects

More support and information

NICE (2007) Laparoscopic cerclage for prevention of recurrent pregnancy loss due to cervical incompetence, National Institute for Health and Care Excellence, London 

Thakur M, Mahajan K (2020) Cervical Incompetence.Treasure Island (FL): StatPearls Publishing https://www.ncbi.nlm.nih.gov/books/NBK525954/

NHS. Premature labour and birth. https://www.nhs.uk/pregnancy/labour-and-birth/signs-of-labour/premature-labour-and-birth/ (Page last reviewed: 9 December 2020 Next review due: 9 December 2023)

NICE (2015). Preterm labour and birth. National Institute for health and care excellence https://www.nice.org.uk/guidance/ng25

Cancer Research UK. Pregnancy and abnormal cervical cells. https://www.cancerresearchuk.org/about-cancer/cervical-cancer/treatment-for-abnormal-cervical-cells/pregnancy (Page last reviewed: 10 March 2020 Next review due: 10 March 2023)

NHS. Abortion risks. https://www.nhs.uk/conditions/abortion/risks/ (Page last reviewed: 24 April 2020 Next review due: 24 April 2023)

Ewington LJ, Quenby S. Full Dilatation Caesarean Section and the Risk of Preterm Delivery in a Subsequent Pregnancy: A Historical Cohort Study. J Clin Med. 2020 Dec 10;9(12):3998. doi: 10.3390/jcm9123998. PMID: 33321784; PMCID: PMC7763432.

Anum EA, et al. Connective tissue and related disorders and preterm birth: clues to genes contributing to prematurity. Placenta. 2009;30(3):207-215. doi:10.1016/j.placenta.2008.12.007

British National Formulary. Diethylstilbestrol. https://bnf.nice.org.uk/drug/diethylstilbestrol.html

Song RK, et al. Post-cerclage ultrasonographic cervical length can predict preterm delivery in elective cervical cerclage patients. Obstet Gynecol Sci. 2016;59(1):17-23. doi:10.5468/ogs.2016.59.1.17
Royal College of Obstetricians & Gynaecologists (2018) Cervical stitch. https://www.rcog.org.uk/en/patients/patient-leaflets/cervical-stitch/

Review dates
Reviewed: 03 November 2021
Next review: 03 November 2024