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

To assess whether cervical cerclage in women deemed to be at increased risk of cervical incompetence prolongs pregnancy and thereby improves fetal and neonatal outcome.

Multicentre randomised controlled trial.

Hospitals in the United Kingdom, France, Hungary, Norway, Italy, Belgium, Zimbabwe, South Africa, Iceland, Ireland, the Netherlands and Canada.

One thousand two hundred and ninety-two pregnant women whose obstetricians were uncertain whether to recommend cervical cerclage, most of whom had a history of early delivery or cervical surgery.

Cervical cerclage was compared with a policy of withholding the operation unless it was considered to be clearly indicated.

Delivery before 33 completed weeks, preterm delivery (< 37 weeks), and vital status of the baby after completion of the pregnancy.

The overall preterm delivery rate was 28%. There were fewer deliveries before 33 weeks in the cerclage group (83 (13%) compared with 110 (17%), P = 0.03) and this difference reflected deliveries characterised by features of cervical incompetence (painless cervical dilatation and prelabour rupture of the membranes). There was a corresponding difference in very low birthweight deliveries (63 (10%) compared with 86 (13%), P = 0.05). The difference in the overall rate of miscarriage, stillbirth or neonatal death (55 (9%) compared with 68 (11%)) was less marked and was not statistically significant. The use of cervical cerclage was associated with increased medical intervention and a doubling of the risk of puerperal pyrexia.

These results suggest that the operation had an important beneficial effect in 1 in 25 cases in the trial (95% confidence interval (CI) 1 in 12 to 1 in 300 sutures). Its use is associated with increased medical intervention and puerperal pyrexia. Nevertheless, this trial suggests that, on balance, cervical cerclage should be offered to women at high risk, such as those with a history of three or more pregnancies ending before 37 weeks gestation.