Cervical Insufficiency and Preterm Birth Risk: When Is Cervical Cerclage Considered?

Cervical insufficiency is a clinical diagnosis without clear boundaries, associated with the cervix softening and shortening or opening before the pregnancy is complete; it is linked to the risk of late miscarriage or preterm birth. In people who had a late miscarriage or preterm birth in a previous pregnancy, the cervix can be assessed with ultrasound; the doctor considers options such as monitoring, medicine treatment or cerclage (a stitch in the cervix) for each person.

What does the cervix do in pregnancy?

The cervix generally stays closed throughout pregnancy and so helps the baby to be carried in the womb.

Why is cervical insufficiency treated as a diagnosis without clear boundaries?

Cervical insufficiency is a clinical diagnosis whose boundaries cannot be clearly drawn, and it is usually made in people with a history of late miscarriage or preterm birth. The strength of the cervix is treated as a continuum, not as two separate categories. The word "insufficiency" does not describe a defect in the person or the womb; it is a medical name for the cervix having difficulty carrying the pregnancy.

Is the cervix the only cause of preterm birth?

Most births before the pregnancy is complete start by themselves; some are births started early for a medical reason, or caesareans. Conditions such as multiple pregnancy, infections, diabetes and high blood pressure are linked with preterm birth, but in many cases no cause can be found. The cervix is only one of the factors that can lead to preterm birth. Not finding a cause does not mean anyone is responsible.

The signs of preterm labour include regular tightening or contractions, a pain like period pain, fluid leaking from the vagina and unusual back pain; if there is a change in the baby's movements you should also contact your health team. If you notice any of these symptoms, you need to contact a health professional without waiting. If you have any of these symptoms and are not sure which group you fall into, treat it as urgent and seek care without delay.

Who may be at increased risk?

Risk factors include having had a late miscarriage or preterm birth before, early rupture of the membranes in a previous pregnancy, damage to the cervix from an earlier procedure or surgery on the cervix, a difference in the structure of the womb or a scar, having had a cerclage before, multiple pregnancy and a short cervix found on ultrasound. Having a risk factor does not mean a preterm birth will happen.

How is the cervix assessed?

In people at risk, the length of the cervix can be measured in the middle of pregnancy with a vaginal ultrasound. Your doctor determines who will be measured, when and how many times. The result alone is not enough to decide; it is interpreted together with your history and other findings, and whether protective treatment is needed is assessed accordingly.

Which options are discussed if the cervix is found to be short?

If your cervix is found to be short on ultrasound, the options include cerclage, medicine treatment given vaginally and close monitoring. Which is suitable varies with your history, the ultrasound findings and the condition of your pregnancy. There are not enough data to compare cerclage with medicine treatment; the superiority of one over the other has not been shown.

What is cerclage and who can it be recommended for?

Cerclage is a stitch placed around the cervix and is mostly done vaginally, less often through the abdomen. Cerclage is considered in these situations: if you have a history such as a late miscarriage or preterm birth; if your cervix is found to be short on ultrasound; if your cervix has begun to open (emergency or rescue cerclage; in this case the risks are higher and the likelihood of benefit is lower). When a stitch cannot be placed vaginally or an earlier stitch has been insufficient, a cerclage through the abdomen can be considered. If there are signs of infection, bleeding, contractions or opening of the membranes, cerclage is generally not recommended.

How is cerclage done and what are its risks?

The procedure is done in the operating theatre under spinal or general anaesthetic and is short; most people go home the same day or the next day. The risks include bleeding, infection, injury to the bladder or cervix, early rupture of the membranes, the stitch not being able to be placed and the procedure not working; preterm birth or late miscarriage can still happen despite the procedure. If labour starts while the stitch is in place, the cervix can be injured.

What does research show about the benefit of cerclage?

Research looks at the effect of cerclage in people with a high risk of preterm birth in a singleton pregnancy. According to the results, cerclage may reduce the likelihood of preterm birth; the likelihood of fever and caesarean birth may increase. No clear difference has been shown in serious newborn illness or in the baby going home healthy. For this reason, which of the options is suitable is determined not only by the average results but according to the person's situation. There is also not yet a consensus on the best technique and timing of the stitch.

How are follow-up after cerclage and removal of the stitch planned?

After cerclage, follow the discharge instructions your doctor gives. The stitch is usually removed in the last part of pregnancy, at the start of labour or during a planned caesarean; if the membranes open without labour, the stitch is mostly removed because of the risk of infection. In a later pregnancy a cerclage can be recommended again.

How can you support yourself?

• Do not miss planned check-ups and cervical measurements.
• Report new symptoms to the health team without delay.
• Go to your appointment with your list of questions.
• Tell the health team about the anxiety or low mood caused by your earlier loss or preterm birth.
• Rather than deciding on your own about activity level, supplements and medicines, follow your doctor's recommendations specific to you.

How can you prepare for the consultation with your doctor?

• Ask how your previous pregnancy history affects the monitoring of this pregnancy.
• Find out when and how your cervix will be measured.
• Discuss which of monitoring, medicine treatment and cerclage is being considered for you and why.
• If cerclage is recommended, ask about the type of procedure, the anaesthetic options and the possible risks.
• Find out which instructions you should follow after discharge and which symptoms mean you should seek care without waiting.