What is the purpose and procedure of a cervical cerclage?

Cervical Cerclage: Purpose and Procedure

Cervical cerclage is a surgical procedure that reinforces the cervix to prevent preterm birth in women with cervical insufficiency, which can significantly reduce preterm birth rates by up to 30% in high-risk patients. 1, 2

Purpose of Cervical Cerclage

• Cervical cerclage aims to prevent second-trimester pregnancy losses and preterm births in women with cervical insufficiency, a condition where the cervix prematurely dilates without contractions 2, 3
• The procedure reinforces the cervix by placing sutures to keep it closed until term, preventing it from opening too early during pregnancy 3, 4
• Cerclage has been shown to decrease preterm birth rates before 37,32,28, and 24 weeks in high-risk patients with short cervical length 1

Types of Cervical Cerclage

History-Indicated Cerclage

• Recommended for women with three or more second-trimester pregnancy losses or extreme premature deliveries without other identifiable causes 2, 3
• Typically performed electively at 13-16 weeks gestation 5, 6

Ultrasound-Indicated Cerclage

• Recommended for women with:
  • Previous preterm birth history and cervical length <25 mm on transvaginal ultrasound 2, 3
  • Not generally beneficial for women without previous preterm birth history unless cervix is extremely short (<10 mm) 2

Emergency/Rescue Cerclage

• Performed when there is asymptomatic dilation of the cervix (≥2 cm) or prolapse of amniotic membranes 5, 3
• Higher risk of infectious complications, but may still prevent imminent delivery 3

Cerclage Procedure

• Most commonly performed transvaginally using the McDonald technique, which involves placing a purse-string suture around the cervix 5, 4
• Transabdominal cerclage is an alternative approach when:
  • Transvaginal cerclage is technically difficult due to cervical conditions 5
  • Previous transvaginal cerclage has failed (delivery before 28 weeks) 3
• Laparoscopic cerclage is an emerging technique showing promising results 5

Monitoring After Cerclage

• The Society for Maternal-Fetal Medicine does not recommend routine surveillance with transvaginal ultrasound after cerclage placement due to insufficient evidence supporting clinical benefit 1, 2
• If assessment is performed, measurements may include:
  • Total length of closed cervix regardless of cerclage sutures 1
  • Length of closed cervix from funneling to cerclage sutures, if funneling is present 1

Cerclage Removal

• Typically removed at 36-37 weeks in women anticipating vaginal delivery 3
• In cases of preterm premature rupture of membranes (PPROM), management is controversial:
  • It is reasonable to either remove the cerclage or leave it in situ after discussing risks and benefits 1, 2
  • Retention may increase latency but also potentially increase infectious morbidity 1

Efficacy and Outcomes

• In high-risk patients with short cervical length, cerclage placement results in a 30% decrease in preterm birth before 35 weeks 1
• Cerclage does not appear to affect the overall progress of labor when women reach term, though there may be a slightly longer time from rupture of membranes to delivery 7
• For women with extremely short cervix (<10 mm), cerclage has been shown to decrease preterm birth at <35 weeks (39.5% vs 58.0%) 2

Potential Pitfalls and Caveats

• Cerclage is not indicated for women without a history of preterm birth who have a sonographic short cervix (10-25 mm) 2
• In twin pregnancies, cerclage benefit is less clear but may be considered with very short cervical lengths (<15 mm) 3
• Rescue cerclage carries a high risk of infectious morbidity to mother and baby and should be considered on an individual basis 3
• After cerclage, bed rest, routine antibiotics, tocolysis, and progesterone are generally not recommended 6

Transvaginal ultrasound is the gold standard for cervical assessment before considering cerclage, as it allows complete visualization of the cervix, including the internal os where changes first occur 1, 8.