Don’t be fooled by Simcox’s CIRCLE trial publication about cerclage. The randomization was between an objective measure as a determinant for an intervention vs individual clinical judgment—for which there were no prescribed criteria.

However, if the intervention is ineffective, then the means of deciding whether to perform the intervention will make no difference to the outcome. The finding of no difference between the 2 arms of the randomized, controlled trial simply reflects the lack of efficacy of the intervention. Moreover, the study numbers were profoundly diluted by inclusion of low- to moderate-risk women and the fact that the majority of women (74%) did not undergo the intervention. Although the authors use the term “high risk of preterm birth” (PTB) in their title and article, <10% of the patients qualified as high risk (≥2 PTB), and only 2% of the patients were very high risk (≥3 PTB).

When the CIRCLE trial commenced in 2003, we already knew from the Cochrane systematic review that there was no evidence of effectiveness for prophylactic cerclage. “Until more data become available cervical cerclage should not be offered to women considered at low or medium risk of second trimester miscarriage or extreme preterm labour.” “Due to the invasive nature of the cervical suture insertion and dubious benefit, future evaluation of effectiveness and safety should only be performed within rigorous randomised controlled trials.”

Simcox et al cites the Fetal Medicine Foundation Second Trimester Screening Group’s rigorous randomized controlled trial of prophylactic cerclage vs no cerclage, which found no significant difference between interventions and control for PTB, nor for perinatal or maternal morbidity, or mortality.

Simcox et al cites the commentary of Berghella and Seibel-Seamon but not the metaanalysis of Berghella et al.

The commentary stated that evidence suggested that transvaginal cerclage probably prevents second-trimester loss/PTB only in women with ≥3 PTB/second-trimester losses and called for rigorous trials. There were only 5 patients meeting these criteria in the Simcox et al study.

The metaanalysis of trials to assess the effect of cerclage on the incidence of PTB in women with a short cervical length on transvaginal ultrasonography showed no benefit or detriment in the total population studied.

The CIRCLE trial was not rigorous, appears to have not afforded care based upon best available evidence in 2003–2006 to the enrolled patients, adds very little to our understanding of the benefits and risks of cerclage, and reminds us that randomizing a decision about an ineffective intervention will make no difference to the outcome.