Cervical insufficiency (sometimes called cervical incompetence) occurs when the neck of the womb (the cervix) softens, shortens and opens without any other symptoms of labour. This may be in the second trimester or early in the third, leading to premature delivery of your baby.
Cervical suture - also called cervical cerclage or cervical stitch - is a stitch placed in/around the cervix. This is to try to prevent late miscarriage or premature birth in women who are felt to be at high risk of cervical insufficiency.
This information is about cervical insufficiency and cervical suture. You may find it helpful if you are, or are planning to become, pregnant and you have previously been diagnosed with cervical insufficiency, have had a late miscarriage or have had a baby born prematurely. You may also find it helpful if you are a partner, relative or friend of someone who has been in this situation.
What is the cervix?
The cervix is the lower part of your womb (uterus) which extends slightly into the top of your vagina. The cervix is often called the neck of the womb.
What is cervical insufficiency?
During pregnancy the neck of the womb (cervix) normally remains closed and 'long', like a tube. As pregnancy progresses and you prepare to give birth, the cervix gradually softens, decreases in length (effaces) and opens (dilates).
Cervical insufficiency (cervical incompetence) occurs when the cervix softens and opens painlessly, without you being in labour, after 12 weeks of pregnancy but well before your baby is due to be born. This may cause your waters to bulge and break through the open cervix, and the baby to be born prematurely. Cervical insufficiency is a painless opening of the cervix. It is not the same as premature labour, where the cervix opens because your womb (uterus) has started to contract, although it tends to lead to premature labour.
It is not usually known why some women have this happen to their cervix. It is thought possible that, in some women, the cervix is not as strong. It is possible that infection, inflammation or previous damage to the cervix can sometimes plays a role. Cervical insufficiency is known to be more likely in women who:
- Have inherited disorders of collagen synthesis (for example, some of the Ehlers-Danlos syndromes).
- Have had surgery such as a cone biopsy on the cervix in the past.
- Have had injuries to the cervix during a previous birth or dilation and curettage (D&C).
- Have some lifelong (congenital) abnormalities of the shape of the womb.
- Have had previous miscarriages in the second trimester, particularly if this has happened more than twice.
- Are known to have had cervical incompetence in a previous pregnancy.
- Have a mother who took the medicine called diethylstilbestrol (DES) while she was pregnant with you. DES was used to prevent miscarriage but has not been used in the UK since 1971. It has, however, been used more recently elsewhere in the world.
How is cervical insufficiency detected?
There are usually no symptoms at all. Some women who have cervical insufficiency do notice vague symptoms, which can include:
- Pelvic pressure.
- Premenstrual-like cramping.
- Vaginal discharge that increases in volume, becomes wetter or changes from clear, white, or light yellow to pink or bloody.
- Losing the mucus plug from the neck of the womb (cervix).
Most women with these symptoms will not have cervical insufficiency. If you are thought to be at risk from cervical insufficiency or premature delivery then your obstetrician or midwife may arrange regular transvaginal ultrasound tests, beginning at 14-16 weeks, to measure the length of your cervix and check for signs of early shortening.
When might a cervical suture be advised?
Having a premature birth or late miscarriage is a devastating experience. You are likely to be worried about a future pregnancy and to wonder how you can make sure this doesn't happen to you again. If this has happened to you, you can be referred to a specialist who will talk to you about plans for a future pregnancy. Depending on your situation, a cervical suture may be one of the options recommended for your next pregnancy.
Planned cervical suture
Cervical suture is generally planned if you are felt to be at high risk of premature labour which could be due to cervical insufficiency. You may be in one of the following situations:
- If you have had previous late miscarriages or premature births (before 34 weeks), you may be offered ultrasound scans between 16 and 24 weeks of pregnancy to measure the length of the neck of your womb (cervix). If the scans show that it has shortened to less than 25 mm, you may be advised to have a cervical suture.
- If you have had three or more late miscarriages or three or more premature births you may be advised to have a cervical suture inserted at about 12-14 weeks of pregnancy even if your cervix is not shortened.
In the cases above you would have a planned cervical suture placed early in the second trimester.
Emergency and rescue cervical suture
Sometimes it is noticed during a vaginal examination or a routine ultrasound scan that your cervix has started to open. Depending on your circumstances, you may be offered an emergency cervical suture. A 'rescue cervical suture' is an emergency suture which is put in when the cervix is partly open and the waters are bulging through."
Emergency cervical suture carries a higher risk of complications than planned cervical suture. If you are in this situation, a senior obstetrician will discuss with you the risks and benefits of having a rescue suture.
If you are more than 24 weeks pregnant then, in the UK, cervical suture is generally not advised. This is because the treatment of premature babies in the UK is of a high standard. It is therefore felt that, at this point, the risks to the baby of attempting to delay labour with an emergency suture (particularly the risk of membrane rupture and infection) are greater than the risks of being born early.
What other treatments might I be offered?
If your pregnancy ultrasound between 16 and 24 weeks of pregnancy happens to reveal that the neck of your womb (cervix) is short, or shortening, but you have not had an early delivery before, you will not usually be offered cervical suture, because you will not be considered at high enough risk of premature delivery to justify the (small but real) risks associated with cervical suture..
In this case you may be offered vaginal progesterone treatment. Evidence suggests that this reduces premature birth in women in whom the cervix is short, even if they have no other reason to think they are at risk of premature birth. Treatment is usually with nightly progesterone pessaries, used up to 34 weeks of pregnancy.
You will be given antibiotic treatment if there is any sign of infection. Some doctors give antibiotics as preventers even when there is no sign of infection - for example, an antibiotic pessary that is inserted for one week of each month to try to prevent an infection happening. There is no evidence that this reduces the risk of early delivery.
The Arabin pessary is a soft silicone bowl-shaped pessary that is inserted into the vagina by your obstetrician and placed so that the cervix sits inside it. It is designed to support and compress the cervix but also to tilt and slightly rotate it. This is believed both to take the pressure off the weakest points in the cervix and to protect the mucus plug from being dislodged. There is increasing evidence that, where the cervix is short, the Arabin pessary can delay labour.
Different-sized pessaries are available, and the device is removed at 37 weeks, or when you go into labour if this is sooner.
How is a cervical suture put in?
In cervical cerclage a stitch (suture) consisting of a band of strong thread is placed around the neck of the womb (cervix). It is usually done sometime between 12 and 24 weeks of pregnancy. Very occasionally it is done as an emergency, usually up to 24 weeks. Rarely, as the risks to mother and baby are greater, it is offered up to 28 weeks, although more commonly in countries in which the outcomes for babies born at 24-28 weeks are less good than in the UK.
You may be offered one of two different techniques (the Shirodkar suture or the McDonald suture) but the principles are similar. The Shirodkar suture is placed a little higher and deeper than the McDonald. The procedure uses a band of strong thread being stitched around your cervix to reinforce it and help hold it closed.
A cervical suture is usually done as an outpatient or day-case procedure using a spinal anaesthetic. In the operating theatre, your legs will be put in supports. The doctor will insert a speculum (a plastic or metal instrument used to separate the walls of the vagina) into the vagina and put the suture around the cervix. The procedure should take less than 30 minutes.
Afterwards, you may be given antibiotics to help prevent infection and you will be offered medication to ease any discomfort. You are likely to be able to go home the same day. You will need to take things easy for a few days and may experience light bleeding or cramping.
After this you should get back to normal. Having sex (intercourse) may be continued when you feel comfortable to do so, unless your doctor advises otherwise. An exception is after emergency cervical cerclage, where your doctor may suggest avoiding sex for a time, sometimes up to 32-34 weeks of pregnancy.
Are cervical sutures sometimes inserted through the abdomen?
Yes, very rarely a third technique, in which the suture is put in abdominally through open surgery, is used. This can be done in between pregnancies, or early in the first trimester, before 12 weeks. It is offered in cases where you have had previous premature deliveries and a cervical suture has been recommended, but it is not technically possible to perform the process vaginally.
This type of suture is usually left in place, meaning that your baby needs to be born by planned caesarean section.
How effective is the cervical suture?
The cervical stitch (suture) appears most effective when put in in a planned way in women who are at high risk of premature delivery of their baby.
The research into how well a cervical suture stops preterm birth is still inconclusive, but women who have a cervical suture carry their babies for longer than those who do not. The suture is thought to reduce the risk of early delivery (delivery before 37 weeks) in high-risk women by 30-50% .
What are the risks of having a cervical suture?
In planned cervical stitch (suture) the risk of complications is low. There is a small risk that your bladder or the neck of your womb (cervix), or a small blood vessel, may be damaged at the time of the operation. Rarely, your membranes may rupture during or just after the procedure, and there is a very small risk of infection inside the waters in the womb (uterus). A planned cervical suture does not increase your risk of miscarriage, or premature labour. It does not increase your risk of having to be started off in labour (be induced) or needing a caesarean section.
The risks associated with planned cervical suture go up slightly with gestation, so a planned suture has the least risk of complications if put in as early as possible.
For emergency cervical suture the risk of complications is much higher, particularly if your cervix has not only shortened but is already partly open when the suture is put in. There is a higher rate, in particular, of the waters breaking and of infection developing. In some cases this may be because the procedure was done so late that the waters were breaking anyway. However, for this reason emergency cervical suturing is a less common procedure.
Are there situations when a cervical suture would not be put in?
Sometimes a cervical stitch (suture) is not advised. It will not normally improve the well-being of your baby/babies and may carry risks to you if:
- You are more than 24 weeks pregnant (in some countries it is used up to 28 weeks, but where care of premature babies is good it is felt to be safer for the baby to be born at 24-28 weeks than for the mother to have the suture).
- You are carrying twins or triplets.
- Your womb (uterus) is an abnormal shape.
- An ultrasound scan done for another reason happens to show that the neck of your womb (cervix) is short, but you have not previously had an early delivery.
- You have had treatment to the cervix for an abnormal smear.
A suture absolutely cannot be put in if:
- You are already in labour or your waters have broken.
- You have signs of infection in your womb.
- You have vaginal bleeding.
- There are concerns about your baby's well-being.
If any of these apply to you but you are thought to be at risk of premature labour, you will be closely monitored. This may include regular vaginal ultrasound scans to measure the length of your cervix until 24 weeks of pregnancy. You may be offered corticosteroid injections after 23 weeks to increase the chance of your baby surviving if born early. Find out more about corticosteroids in pregnancy to reduce complications from being born prematurely.
How is a cervical suture removed?
The cervical stitch (suture) is not made of dissolving material; it stays in place in the neck of the womb (cervix) until it is removed. It is usually removed at 36-37 weeks, or if you go into labour before then, as if it was left in place it could injure the cervix as it opens. The McDonald suture can usually be removed quickly without anaesthetic during a vaginal examination, but the deeper, Shirodkar suture may need a short anaesthetic for removal. This suture can sometimes be left in place if you are having a planned caesarean delivery and hope to have further pregnancies.
You may have a small amount of bleeding afterwards. Any red bleeding should settle within 24 hours but you may have a brownish discharge for longer than this. If you go into labour before the cervical suture has been removed, it is very important to have it removed promptly to prevent it causing damage to your cervix. If you think you are in labour, contact your maternity unit at once and explain the situation.
If your waters break early but you are not yet in labour, the suture will usually be removed because of the increased risk of infection. The timing of this will be decided by the team looking after you, but you will generally need to go into the labour unit to be seen.
Once the suture has been removed, do I need to take any special precautions?
No, when the cervical stitch (suture) has been removed it has served its purpose. You may go into labour soon after it has been removed, as many women do - but this may does not always happen immediately.
Full-term pregnancy is an average of 40 weeks from your last period and as the suture is removed at 37 weeks, if removing the suture doesn't trigger labour you will be in the same boat as everyone else, and may even go beyond the delivery date before labour begins.
Further reading and references
Preterm labour and birth; NICE Guidelines (November 2015 - last updated August 2019)
Preterm labour and birth; NICE Quality Standard, October 2016
Dodd JM, Jones L, Flenady V, Cincotta R, Crowther CA; Prenatal administration of progesterone for preventing preterm birth in women considered to be at risk of preterm birth. Cochrane Database of Systematic Reviews 2013, Issue 7. Art. No.: CD004947. DOI: 10.1002/14651858.CD004947.pub3.
Arabin, B. and Alfirevic, Z. (2013); Cervical pessaries for prevention of spontaneous preterm birth: past, present and future. Ultrasound Obstet Gynecol, 42: 390–399. doi:10.1002/uog.12540