Outcomes following elective cerclage versus ultrasound surveillance in women with one prior preterm event

Preterm birth, defined as delivery before 37 weeks' gestation, is a major obstetric challenge and is associated with serious long-term complications in those infants that survive. Preventative management includes cervical cerclage, either as an elective procedure or performed following transvaginal ultrasound surveillance and shortening of the cervix (≤25 mm). Significant questions remain regarding the optimal management, target population and technique. Therefore, this study aimed to assess differences in risk factors and pregnancy outcomes for women who received an elective cerclage versus ultrasound surveillance, following one prior premature event (spontaneous preterm birth/second trimester loss).

Women were retrospectively identified from St Thomas's Hospital Preterm Birth Clinical Network Database. Women who had one prior premature event (between 14⁺⁰ and 36⁺⁶ weeks' gestation) were included and they were separated into those that an elective cerclage and those who underwent ultrasound surveillance to assess differences in demographics, pregnancy risk factors and preterm birth outcomes. We excluded women who received other preventative therapies. We also separately analysed those women who required an ultrasound-indicated cerclage, comparing the differences between women that delivered preterm and term.

We collected data from 1077 women who had a prior preterm event. 66 women received an elective cerclage. 11.4% of women who had ultrasound surveillance received an ultrasound indicated cerclage. Women with a prior history of mid-trimester loss, instead of preterm birth, were more likely to receive an elective cerclage. The mean gestational age of delivery was similar between those women who received an elective cerclage and those who had ultrasound surveillance with and without an ultrasound-indicated cerclage (38⁺¹ vs 37⁺¹), however, preterm birth rates <37 weeks' were twice as high in this ultrasound group (OR 2.3 [1.1-4.5], p = 0.02). In those women that do require an ultrasound-indicated cerclage, 50.4% deliver preterm.

In conclusion, this study shows that in women with one prior preterm event, both history-indicated cerclage and ultrasound surveillance are appropriate management options. The majority of women undergoing ultrasound surveillance did not require a cerclage and so avoided the potential perioperative complications of cerclage insertion. However, those that did require an ultrasound-indicated cerclage were at high risk of preterm birth so should be followed up closely to enable adequate preterm birth preparation. Further prospective studies comparing history indicated cerclage and US surveillance in women with one prior preterm event are necessary.