High versus low vaginal cerclage: no difference in pregnancy loss in C-STICH

Design

Secondary analysis of a multicentre randomised trial; height not randomised

Population

1,995 UK women with transvaginal cerclage at high risk of preterm birth

Primary outcome

Pregnancy loss (miscarriage or perinatal death)

Effect

6.5% vs 7.3%, aRR 0.88 (95% CI 0.57-1.34); birth before 32 weeks aRR 0.57 (0.37-0.86)

C-STICH randomised 2,048 UK women at high risk of preterm birth to cerclage suture material. This secondary analysis looked at cerclage height instead, which was left to the surgeon: 24% of 1,995 women had a high cerclage with bladder dissection and 76% a low one without.

Pregnancy loss was similar (6.5% vs 7.3%; adjusted RR 0.88, 95% CI 0.57-1.34). High cerclage was associated with a mean gain of 0.5 weeks and fewer births before 32 weeks (adjusted RR 0.57, 0.37-0.86).

Surgeons have long argued about whether the extra dissection of a high vaginal cerclage is worth it. On the outcome that matters most, loss of the pregnancy, it made no clear difference.

The signal on early preterm birth is interesting but not decisive, because height was not randomised and surgeons may have chosen the high approach for different women.

• Low vaginal cerclage remains a reasonable default for most surgeons.
• Where the operator is experienced with bladder dissection, the possible reduction in births before 32 weeks is worth discussing.
• Record cerclage height in the operation note; it is rarely documented and matters for the next pregnancy.
• The ACOG Clinical Practice Guideline on obstetric cerclage (September 2026) is the reference for indications.

Why it matters

The extra dissection of a high cerclage has not been shown to reduce pregnancy loss, which removes pressure on surgeons to adopt it.

Don't overread it

Cerclage height was not randomised, so the fewer births before 32 weeks may reflect which women surgeons chose for each technique.

The statistics, in plain English

The confidence interval for pregnancy loss runs from a 43% reduction to a 34% increase, so the study cannot rule out a real difference in either direction. The preterm-before-32-weeks result excludes 1.0, but as a secondary outcome in a non-randomised comparison it is a hypothesis, not proof.

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