Indications for Cervical Cerclage: A Practical Algorithm
Three Types of Cerclage Based on Clear Clinical Criteria
Cerclage placement follows three distinct pathways: history-indicated (12-14 weeks), ultrasound-indicated (when cervix ≤25 mm before 24 weeks), and examination-indicated (when cervical dilation detected before 24 weeks). 1, 2, 3
History-Indicated Cerclage (Prophylactic)
When to Place:
Specific Indications:
- Three or more prior second-trimester losses or extreme premature deliveries without other identifiable causes 1, 2, 5
- Classic cervical insufficiency features: Prior second-trimester loss with painless cervical dilation in the absence of labor, rupture of membranes, or placental abruption 2, 4
- Prior cerclage placement due to painless cervical dilation in second trimester 5
Critical Pitfall:
- Do NOT delay cerclage until the gestational age of prior loss (e.g., waiting until 18 weeks if prior loss occurred at 18 weeks)—this is too late as cervical changes may already be underway 4
- Avoid history-indicated cerclage after prior previable PPROM unless classic cervical insufficiency features are present, as one study showed increased odds of preterm birth 2
Ultrasound-Indicated Cerclage
Surveillance Protocol:
- Begin serial transvaginal ultrasound at 14-16 weeks in high-risk patients (1-2 prior second-trimester losses or preterm births) 1
- Transvaginal ultrasound is the reference standard—superior to clinical examination alone 1
Specific Placement Criteria:
- Cervical length ≤25 mm before 24 weeks in singleton pregnancy with history of spontaneous preterm birth 1, 2
- Particularly beneficial when cervical length <10 mm: decreased preterm birth at <35 weeks (39.5% vs 58.0%) 1, 2
What NOT to Do:
- Do NOT place cerclage for cervical length 10-25 mm in patients WITHOUT prior preterm birth history—meta-analysis shows no benefit 1, 2
- Do NOT place cerclage at arbitrary gestational ages without objective cervical shortening 1
Alternative Management:
- For cervical length 21-25 mm: offer vaginal progesterone 200 mg daily as alternative or adjunct 1
- For cervical length ≤20 mm with 1-2 prior losses: prescribe vaginal progesterone first (GRADE 1A recommendation) 1
- Consider ultrasound-indicated cerclage only if cervix shortens to <10 mm despite progesterone 1
Examination-Indicated Cerclage (Emergency/Rescue)
When to Perform Physical Examination:
- When ultrasound shows cervical length <11-15 mm, as 30-70% will have cervical dilation ≥1 cm on examination 1
Specific Placement Criteria:
- Cervical dilation detected on physical examination before 24 weeks in the absence of contractions 1, 3
- Cervical dilation <4 cm without contractions before 24 weeks 6
Key Consideration:
- This represents the most urgent cerclage indication, requiring prompt evaluation and placement if criteria met 3
Post-Cerclage Management
Adjunctive Therapy:
- Add vaginal progesterone 200 mg daily after cerclage placement: reduces spontaneous preterm birth at <34 weeks (2.2% vs 18.4%) and <37 weeks (9.1% vs 29.7%) 1, 2, 4
Surveillance:
- Serial ultrasound monitoring after cerclage is NOT routinely recommended due to insufficient evidence supporting clinical benefit 7, 2, 4
- If surveillance performed, shorter cervical length below cerclage and funneling associate with higher preterm birth rates, but no proven intervention exists 7
What to Avoid:
- Do NOT use 17-alpha hydroxyprogesterone caproate (17-OHPC) for short cervix treatment (GRADE 1B recommendation against) 1
- Do NOT place cervical pessary due to conflicting data and safety signals including increased perinatal mortality 1
- Do NOT routinely use antibiotics, tocolysis, or bed rest after cerclage 5
Special Populations
Multiple Gestations:
- Do NOT place cerclage in multiple gestations, even with history of preterm birth or short cervix—no benefit demonstrated 5, 6
Post-Conization:
- Use serial cervical length measurements rather than automatic cerclage placement 1
Abdominal Cerclage:
- Consider when prior vaginal cerclage unsuccessful or after trachelectomy 6