Background Cervical surgery is a risk factor for preterm birth,1 but the management of women with prior preterm birth with cervical surgery is not clear.2 Cerclage could be more appropriate in this group as an intervention, as this is a logical treatment for a deficient cervix. We determined whether history of cervical surgery increased risk over history of early pregnancy delivery.

Methods Data from 653 women referred to a Preterm Surveillance clinic, who had 1 or 2 previous preterm births/midtrimester loss without cerclage were analysed. 52 women with preceding cervical surgery and a PTB were compared to 601 matched controls (prior PTB but no surgery). Spontaneous delivery <30, 34 and 37 weeks in both groups were compared (Chi square).

Results Overall 228 (34.9%), 67 (10.2%) and 34 (5.2%) of women delivered <37, 34 and 30 weeks respectively. The rate of preterm birth and midtrimester losses were similar (chisquare, NS) between controls and surgery groups: 35.3 vs 30.8% (<37/40), 10.1 vs 11.5% (<34/40) and 4.9 vs 7.7% (<30/40).

Conclusions A history of previous cervical surgery does not increase risk further in women with prior preterm birth/midtrimester loss. Management should be based on previous pregnancy history. Current RCOG cerclage guidelines can be followed (i.e. rely on previous pregnancy history) though further research is needed to evaluate whether these women benefit from cerclage at a lower threshold.