Cervical cerclage is a surgical procedure that is carried out during pregnancy to position a stitch (suture) around the neck of the womb (cervix). The purpose is to give mechanical support to the cervix and so reduce the risk of preterm birth. During normal pregnancy the neck of the cervix stays tightly closed, allowing the pregnancy to reach full term. Towards the end of pregnancy the cervix starts to shorten and progressively becomes softer preparing for normal labour and delivery. Sometimes, the cervix starts to shorten and dilates too early, causing either late miscarriage or preterm birth.
This review included a total of 12 randomised controlled studies involving 3328 pregnant women at high risk of pregnancy loss. When cerclage was compared with no treatment (nine trials), there was no clear difference in the number of babies dying before (as a result of miscarriages, stillbirths) or around the time of birth or neonatal illness, despite a clear reduction in the number of preterm births. More women needed caesarean section and experienced side effects (vaginal discharge, bleeding, fever/pyrexia) with the procedure, although side effects were not serious.
One study in women with a short cervix detected by transvaginal ultrasound compared cerclage with weekly intramuscular injections of 17 α-hydroxyprogesterone caproate and did not find any differences in obstetric outcomes for the mother and newborn. Two studies compared the benefits of performing cerclage based on a previous history with cerclage if the cervix was found to be short using transvaginal ultrasound. Again, there were no significant differences between these two management protocols.