Elective cervical cerclage versus serial ultrasound surveillance of cervical length in a population at high risk for preterm delivery

OBJECTIVE: To compare pregnancy outcome for women at risk of preterm delivery undergoing elective cervical cerclage in the first trimester or serial transvaginal assessment of cervical length with cerclage only if indicated (control cases). DESIGN: A matched case control study. SETTING: Prematurity clinic at two London teaching hospitals. POPULATION: Women at high risk for preterm delivery. METHODS: Cases of elective cervical cerclage were matched for maternal age, ethnic group, previous cervical surgery, previous second trimester loss and early preterm delivery to women undergoing serial ultrasound surveillance of cervical length. Pregnancy outcome data was collected. Data was analysed using Fisher's exact, Mann-Whitney and Student's t-tests. MAIN OUTCOME MEASURES: Gestation at delivery, rate of delivery <24, 24-32 and 32-37 weeks gestation. RESULTS: Thirty-nine cases of elective cervical cerclage were matched to control cases. Both groups were similar for maternal age, ethnic group, previous cervical surgery, previous second trimester loss and early preterm delivery. Cervical cerclage was performed in 14 (36%) of the control cases due to cervical changes. There was no significant difference in median gestation at delivery (266 days versus 260 days P=0.9), number delivering <24 weeks (15% versus 13% P=0.9), at 24-32 weeks (7.5% versus 15% P=0.6) and at 32-37 weeks (15% versus 13% P=0.9). CONCLUSION: Serial transvaginal ultrasound surveillance of cervical length in women at high risk of preterm delivery appears to reduce cerclage rates without compromising pregnancy outcome. A large multicentered randomised trial is required to confirm these findings.