Maternal-Fetal Medicine
Prophylactic & Emergency
Cerclage
Understanding Your Options
◆ Patient Education & Counseling
Foundation
What is Cervical Insufficiency?
The cervix is the lower part of the uterus that normally stays closed until labor.
Definition The cervix opens painlessly in the second trimester — without contractions or labor.
Also called Cervical incompetence or cervical weakness
Pregnant anatomy illustration
Clinical Significance
Why Does it Matter?
Cervical insufficiency can lead to pregnancy loss or very early preterm birth.
Gestational AgeClinical ConcernOutcome Risk
14 – 20 weeksSecond-trimester pregnancy lossHigh
20 – 24 weeksPeriviable preterm birthHigh
24 – 34 weeksPreterm birth with NICU careModerate
ACOG Practice Bulletin No. 142 | SMFM Guidelines
Indications
Who Might Need a Cerclage?
History-Indicated (Prophylactic) ≥1 prior painless second-trimester loss or prior cerclage for same indication
Ultrasound-Indicated Prior preterm birth <34 weeks + cervical length <25 mm before 24 weeks
Physical Exam-Indicated (Rescue) Painless cervical dilation found on examination before 24 weeks
Decision tree for cerclage placement
Procedure Types
Types of Cerclage
Suture placement diagram for transvaginal and transabdominal cerclage
McDonald Cerclage Purse-string suture at the cervicovaginal junction. Most common. Easily removable in office.
Shirodkar Cerclage Suture placed higher, closer to the internal os. Requires submucosal dissection.
Transabdominal Cerclage Placed at the cervico-isthmic junction. Reserved for cases where vaginal approach fails or is not feasible.
Surgical Approach
Vaginal vs. Abdominal Cerclage
Indications for vaginal and abdominal cerclage
Prophylactic Cerclage
History-Indicated Cerclage
Placed early in pregnancy to prevent recurrence of cervical insufficiency.
8
8–12 wks
Consider for
extreme PTB
(<28 wks history)
13
13–14 wks
Optimal timing
for prophylactic
cerclage
16
16–24 wks
Ultrasound-
indicated
window
24
<24 wks
Rescue cerclage
considered up
to this point
36
36–37 wks
Cerclage
removal
Evidence Level: Grade 1A (High Benefit) Mean pregnancy prolongation: approximately 21 weeks (ACOG PB 142)
Ultrasound-Indicated Cerclage
Short Cervix on Ultrasound
Ultrasound showing short cervix at 17 weeks 3 days measuring 0.7 cm
Criteria (SMFM) Singleton pregnancy + prior spontaneous PTB <34 weeks + CL <25 mm before 24 weeks
Important Limitation Cerclage is NOT recommended for short cervix alone without prior PTB history (Grade 1B)
Not for Twins Evidence does not support cerclage in twin gestations (Grade 1B)
Cervical Changes
What is Cervical Funneling?
The internal cervical os begins to open, allowing amniotic membranes to protrude into the cervical canal.
Sonographic Definition Protrusion of membranes >5 mm into the internal os, usually with CL <25 mm
Measurement Formula % Funneling = A ÷ (A+B) × 100
A = funnel length  |  B = functional cervical length
Cervical funneling measurement diagram
Cervical Changes
Progressive Cervical Dilation
Four stages of cervical incompetence and funneling
Stage a Normal closed cervix with intact internal os
Stage b Early funneling — internal os begins to open
Stage c Progressive funneling with shortened functional length
Stage d Advanced dilation — membranes at or beyond external os
Emergency / Rescue Cerclage
Physical Exam-Indicated Cerclage
Before
Ultrasound before rescue cerclage showing prolapsed membranes
Prolapsed membranes visible at cervical os
After
Ultrasound after rescue cerclage showing cervix at 16mm
Cervix restored to 16 mm after cerclage
Evidence Level: Grade 2C Mean pregnancy prolongation: approximately 10 weeks  |  Success rates decrease after 23 weeks
Clinical Decision-Making
When Cerclage is NOT Recommended
⚠
Active LaborContractions present at time of evaluation
⚠
ChorioamnionitisClinical signs of intra-amniotic infection
⚠
Active Vaginal BleedingContinuous unexplained hemorrhage
⚠
Fetal Demise or Lethal AnomalyNon-viable fetal status
⚠
PPROM (Relative Contraindication)Management individualized based on infection/labor status
⚠
Twin GestationNo evidence of benefit for cerclage in twins (Grade 1B)
Informed Consent
Risks of the Procedure
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Membrane RuptureHigher risk with rescue cerclage due to prolapsed membranes
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InfectionChorioamnionitis — primary risk, especially in emergent settings
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Cervical TraumaLaceration risk if labor begins with stitch in place
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AnesthesiaPerformed under regional (spinal or epidural) anesthesia
No Evidence Supports Routine bed rest, prophylactic antibiotics, or tocolytics after cerclage (ACOG PB 142)
Post-Procedure Care
What to Expect After Cerclage
Summary
Cerclage at a Glance
Feature History-Indicated Ultrasound-Indicated Rescue (Exam-Indicated)
Indication ≥1 prior 2nd-trimester loss (painless) Prior PTB <34 wks + CL <25 mm Painless dilation 1–4 cm before 24 wks
Optimal Timing 13–14 weeks 16–23⁶⁄₇ weeks 16–23⁶⁄₇ weeks
Evidence Level Grade 1A Grade 1B Grade 2C
Mean Prolongation ~21 weeks Variable ~10 weeks
Sources: ACOG Practice Bulletin No. 142  |  SMFM Consult Series  |  NICE Guidelines
Your Care Team
We Are Here With You
Cerclage is a well-established, evidence-based procedure. Our goal is to support you and your pregnancy with the best available care.
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