Reviewed April 2014, next review April 2017

Explaining premature birth - risks and causes

Cervical insufficiency (also known as incompetent cervix/cervical weakness)

The cervix is the small canal at the base of the womb that connects it to the vagina. It is also known as the neck of the womb.

When a normal pregnancy reaches full term the cervix begins to dilate (open) and efface (shorten) to allow the baby out. Cervical insufficiency (or cervical weakness/incompetent cervix) is the term for when this happens early without labour or contractions in the second trimester. It can lead to the waters breaking and late miscarriage or premature birth.

Causes of cervical insufficiency

The cervix may be naturally weak, or the weakness may have been caused during previous pregnancy, previous obstetric trauma or childbirth.

Research shows that infection caught during pregnancy is linked to the cervix shortening and opening but it is not clear whether the infection causes the cervix to open or the cervix is opening because of the infection

Am I at risk of cervical weakness?

You are considered to be at higher risk of having cervical weakness if you have previously had one or more premature births or miscarriages during the second trimester or third trimester. Previous cervical biopsy, or other surgery involving the cervix is also a risk factor.

Treatment for cervical weakness - the cervical stitch/cerclage

If your healthcare team are concerned about your cervix, you may be offered an internal scan to look at the neck of the womb more closely during your pregnancy.

If you have had one or more premature babies/late miscarriages or cervical surgery in the past and your cervix is getting shorter in early pregnancy, or if you have had a number of premature deliveries but your cervix has not shortened, you may be offered a cervical stitch (also known as a cerclage or cervical suture).

This is a special stitch that is put around your cervix to keep it closed. It can be put in before or during pregnancy. After the operation you may have some cramps similar to period pains, and you may have bleeding and spotting for a few days.

The stitch is usually removed at around 37 weeks so you can give birth. If you go into labour before then, it will be taken out immediately.

The cervical stitch can be put at the top (abdominal) or bottom (vaginal) of your cervix. It is usually put in under regional anaesthetic, such as an epidural, which means you are awake but can't feel anything.

The research on the effects of the stitch is still uncertain but so far it shows that most women who have had cerclage have carried their babies to full term. In a small number of women however the stitch does not prevent the waters from breaking and causing a miscarriage or preterm birth. Other rare complications include infections or excessive bleeding.

Cervical stitch illustration


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

Cockwell HA, Smith GN (2005) Cervical incompetence and the role of emergency cerclage. J Obstet Gynaecol Can. 2005 Feb;27(2):123-9

Liddiard A, Bhattacharya S (2011) Elective and emergency cervical cerclage and immediate pregnancy outcomes: a retrospective observational study, JRSM Short Rep. Nov 2011; 2(11): 91.


The causes and problems of premature birth

Your premature baby:

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Feedback on health information

'When I was around 20 I had some pre-cancerous cells and had laser treatment, and that could have made my cervix incompetent. When I was pregnant it never entered my head. I don't think I was told at the time to worry about it in future.'


'I'd had two miscarriages, but with my next baby I was given an early cervical stitch and carried her to full term.'



The cervical stitch was invented in the 1950s.

‘Because of my history, I was booked in to have a vaginal stitch really early – at nine weeks. I had the epidural, but when the doctor attempted to do the stitch, he said there wasn’t enough cervix to work with. So I went in a few days later and had an abdominal stitch done under general anaesthetic. Having major surgery when you’re pregnant feels odd, but I wanted it. In the end I went to 39 weeks and four days.’