Cervical Cerclage
Terminology
Ambiguous older terms are replaced with indication-based names: history-indicated (prophylactic, based on history, placed 11–14 weeks in asymptomatic women), ultrasound-indicated (therapeutic, for cervical shortening on TVUS, no exposed membranes, surveillance usually 14–24 weeks), and emergency/rescue cerclage (salvage suture with exposed membranes in the vagina, considerable up to 27⁺⁶ weeks). Transvaginal technique is subdivided into McDonald (low, no bladder mobilisation) and high transvaginal, e.g. Shirodkar (with bladder mobilisation, above the cardinal ligaments); transabdominal cerclage is placed via laparotomy/laparoscopy at the cervico-isthmic junction.
Indications
- History-indicated: offer to singleton pregnancies with ≥3 previous preterm births and/or second-trimester losses [Grade B]; benefit was not demonstrated with only one or two prior losses, so cerclage should not be routinely offered below this threshold [Grade B].
- Ultrasound-indicated: an incidentally short cervix (<25mm) with no other risk factors does not warrant cerclage [Grade B]. In women with a history of spontaneous second-trimester loss or preterm birth under serial TVUS surveillance, offer cerclage if cervical length is ≤25mm before 24 weeks [Grade A]. Funnelling alone, without a short closed length, is not an indication [Grade C].
- Emergency cerclage: decision individualised by a senior obstetrician [Grade D]. May delay birth by ~34 days and halve birth <34 weeks, though evidence of neonatal benefit is limited [Grade B]. Cervical dilatation >4cm or membrane prolapse predicts failure [Grade D]; rarely justified beyond 24 weeks (risk of iatrogenic membrane rupture).
- Not recommended: cerclage in multiple pregnancy without additional risk factors [Grade B]; role uncertain in other high-risk groups without additional risk factors (Müllerian anomalies, prior cervical excisional surgery, prior multiple D&E) [Grade B].
- Contraindications: active preterm labour, chorioamnionitis, continuing bleeding, PPROM, fetal compromise, lethal fetal anomaly, fetal death [GPP].
Technique and Timing
Non-absorbable suture, surgeon's discretion [GPP]. Choice of high vs low transvaginal insertion is at the surgeon's discretion [Grade C], but the suture should be placed as high as practically possible. Transabdominal cerclage may be discussed after a previous unsuccessful transvaginal cerclage [Grade A — corrected 2023 from Grade D]; the MAVRIC trial showed preterm birth <32 weeks of 8% (abdominal) vs 33% (low vaginal), NNT ≈4. Pre-conceptual insertion is preferred where feasible [GPP]; laparoscopic and open approaches have similar efficacy, with fewer complications laparoscopically [Grade C]. Elective transvaginal cerclage can be a day case [Grade C]; anaesthesia choice (general/regional) is joint decision-making [Grade B]. No routine perioperative tocolysis [GPP]; antibiotics at operator discretion [Grade C]. Remove transvaginal cerclage electively at 36⁺¹–37⁺⁰ weeks, or promptly if labour is established [GPP]. Transabdominal cerclage mandates caesarean birth, and the suture may be left in for future pregnancies [GPP]. After PPROM, delayed removal for 48 hours (steroids/in-utero transfer) may be considered between 24–34 weeks without infection [GPP], but prolonged retention is not recommended given sepsis risk with minimal latency benefit.
Adjuncts (Not Routinely Recommended)
Bed rest, coital abstinence, routine progesterone supplementation after cerclage, routine post-cerclage cervical-length surveillance, reinforcing (repeat) sutures after a shortening cervix following history-indicated cerclage, and routine fetal fibronectin testing are all not routinely recommended [GPP/Grade C/D] — evidence of benefit is lacking for each. An Arabin pessary or progesterone alone is not proven more or less effective than cerclage [Grade C].
High-Yield Exam Points
- Nomenclature: history-indicated (11–14 weeks, ≥3 prior losses), ultrasound-indicated (CL ≤25mm before 24 weeks + relevant history), emergency (exposed membranes, up to 27⁺⁶ weeks).
- Incidental short cervix with no other risk factors → no cerclage (Grade B) — classic exam distractor.
- MAVRIC trial: transabdominal cerclage after failed transvaginal cerclage is now Grade A (corrected from D in 2023); NNT ≈4 to prevent one preterm birth <32 weeks.
- Emergency cerclage prolongs pregnancy ~34 days; dilatation >4cm or membrane prolapse predicts failure.
- Transvaginal cerclage removed electively 36⁺¹–37⁺⁰ weeks; abdominal cerclage always requires caesarean.
- Not recommended in multiple pregnancy without added risk factors.
- Routine progesterone, bed rest, abstinence, and post-cerclage surveillance/fibronectin are all "don't over-manage" negatives — recurring exam theme.
Source: RCOG Green-top Guideline No. 75 (June 2022 (2nd edition; Shennan, Story — BJOG 2022;129:e178–e210). Corrected 10 March 2023 (a key recommendation's evidence grade was raised from D to A — see Technique below). Reviewed February 2025, validity extended to 2027. Replaces the 1st edition, Green-top Guideline No. 60 (2011). Supplements NICE NG25 *Preterm Labour and Birth*.)
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