Interim report of the Medical Research Council/Royal College of Obstetricians and Gynaecologists multicentre randomized trial of cervical cerclage. MRC/RCOG Working Party on Cervical Cerclage.

Overall 905 pregnant women whose obstetricians were 'uncertain' whether to recommend cervical cerclage, chiefly because of a history of early delivery or cervical surgery, were randomly allocated to cerclage or no surgery; 92% were treated as allocated. The overall preterm delivery rate was 30%. The results for those allocated cerclage were marginally statistically significant, more favourable in terms of fewer deliveries before 33 weeks [59 (13%) compared with 82 (18%), P = 0.03] and correspondingly for birthweight under 1500 g [48 (11%) compared with 73 (16%), P = 0.01] and for miscarriage, stillbirth or neonatal death [37 (8%) compared with 54 (12%), P = 0.06]. There were similar numbers of deliveries between 33 and 36 weeks [65 (14%) compared with 64 (14%)]. These results suggest that the operation had an important beneficial effect in one in 20 to 25 cases in the trial. But because the observed differences are not strongly statistically significant and because no such benefit has been seen in other randomized trials, there remains uncertainty about how much (if any) of this apparent benefit is real. So, the trial still remains open for randomization of more women whose obstetricians are uncertain about the advisability of cerclage.