Normally during pregnancy the cervix remains tightly closed until the final few weeks, at which point it softens and shortens in preparation for labour and delivery. Unfortunately, in some cases this happens a lot earlier, increasing the risk of late miscarriage or premature birth.
This condition is known as cervical incompetence or insufficiency; however, with no consistent definition, exact prevalence rates are difficult to deduce. Generally speaking, short means less than 25mm and certain women are at greater risk of experiencing the condition:
- Those who have previously had a late miscarriage (16 weeks plus).
- Those who have previously given birth before 34 weeks gestation.
- Those whose waters have broken before 37 weeks in previous pregnancies.
- Those who have undergone cervical procedures such as a cone biopsy following an abnormal smear test.
Women who fall into these categories will be monitored particularly closely for the duration of their pregnancy.
Managing cervical incompetence
If the cervix does start to soften and shorten, your doctor might suggest mechanical support, in the form of a cervical suture, to reduce the risk of premature labour or miscarriage. This procedure is known as cervical cerclage and is one of the most well-known obstetric surgical techniques.
It is usually performed between weeks 12 and 24 of pregnancy using either a spinal block or a general anaesthetic. A speculum is inserted into the vagina and a stitch is placed around the cervix, pulled tight and tied. The stitch should be removed before delivery, usually between weeks 36 and 37, to avoid damage to the cervix. In some cases, the procedure is performed via the abdomen, rather than the vagina. This might happen if the vaginal method fails or is judged to be too technically difficult. Alternatively, women who have already experienced a number of failed pregnancies might choose to have a stitch put in during the early stages of their pregnancy to reduce the risk of it happening again. A stitch made via the abdomen will stay in place for the duration of the pregnancy and delivery will always be via caesarean.
When is a cervical cerclage not a suitable option?
A cervical cerclage will not be suitable for everyone. If you have already experienced contractions, bleeding, or your waters have broken, your doctor will not perform the technique. Additionally, it is not guaranteed to work and can cause uterine contractions, bleeding and increase the risk of infections. All women should take the time to weight up the potential risks versus the likelihood of success, prior to undertaking the procedure.
It is worth concluding on a positive note though. When a large scale review of over 3500 women was conducted, it was found that cervical cerclage did significantly reduce the likelihood of premature birth and probably also reduced the risk of perinatal death. There was no definitive answer with regards to whether cervical cerclage or progesterone pessary was more successful; however, sometimes the two techniques were used in combination to reduce the risk of late miscarriage or premature delivery.
Nabta is reshaping women’s healthcare. We support women with their personal health journeys, from everyday wellbeing to the uniquely female experiences of fertility, pregnancy, and menopause.
Get in touch if you have any questions about this article or any aspect of women’s health. We’re here for you.
- Alfirevic, Z, et al. “Cervical Stitch (Cerclage) for Preventing Preterm Birth in Singleton Pregnancy.” The Cochrane Database of Systematic Reviews, vol. 2017, no. 6, 6 June 2017, p. CD008991., doi:10.1002/14651858.CD008991.pub3.
- Cervical Stitch. Royal College of Obstetricians & Gynaecologists, www.rcog.org.uk/globalassets/documents/patients/patient-information-leaflets/pregnancy/pi-cervical-stitch.pdf.