OBJECTIVE: Our aim was to assess the association between loop electrosurgical excision procedure (LEEP) and the subsequent risk for spontaneous preterm delivery, with the use of population-based data from various nationwide registries. STUDY DESIGN: The study population consisted of all singleton deliveries in Denmark during a 9-year period, 1997-2005. Information on the deliveries that included different cervical procedures was obtained from various national registries. In all, 552,678 deliveries were eligible for analyses. RESULTS: Of the deliveries in which the mother had no previous LEEP, 18,519 deliveries (3.5%) were preterm; when this data were applied to 530 preterm deliveries (6.9%) that were subsequent to LEEP, the yield was a significantly increased risk of preterm delivery, with an odds ratio of 2.07 (95% CI, 1.88-2.27; LEEP vs no LEEP). CONCLUSION: Our study showed an overall 2-fold increase in the risk of spontaneous preterm delivery in singleton deliveries subsequent to LEEP treatment, even after adjustment for various potential risk factors.