OBJECTIVE: To assess whether loop electrosurgical excision procedure (LEEP) increases the risk for preterm birth before 37 weeks of gestation and clarify whether the increased risk for preterm birth is attributable to the procedure itself or to risk factors associated with cervical dysplasia. DATA SOURCES: Two authors performed a search of the relevant data through February 2013 using PubMed, Embase, Scopus, CENTRAL, and ClinicalTrials.gov. METHODS OF STUDY SELECTION: We included observational studies that compared rates of preterm birth in women with prior LEEP with women with no history of cervical excision. Nineteen of 559 identified studies met selection criteria. TABULATION, INTEGRATION, AND RESULTS: We compared women with a history of LEEP with two unexposed groups without a history of cervical excision: 1) women with an unknown or no history of cervical dysplasia; and 2) women with a history of cervical dysplasia but no cervical excision. The primary outcome was preterm birth before 37 weeks of gestation. Secondary outcomes were preterm birth before 34 weeks of gestation, spontaneous preterm birth, preterm premature rupture of membranes, and perinatal mortality. DerSimonian-Laird random effects models were used. We assessed heterogeneity between studies using the Q and I2 tests. Stratified analyses and metaregression were performed to assess confounding. Nineteen studies were included with a total of 6,589 patients with a history of LEEP and 1,415,015 without. Overall, LEEP was associated with an increased risk of preterm birth before 37 weeks of gestation (pooled relative risk 1.61, 95% confidence interval [CI] 1.35-1.92). However, no increased risk was found when women with a history of LEEP were compared with women with a history cervical dysplasia but no cervical excision (pooled relative risk 1.08, 95% CI 0.88-1.33). CONCLUSION: Women with a history of LEEP have similar risk of preterm birth when compared with women with prior dysplasia but no cervical excision. Common risk factors for both preterm birth and dysplasia likely explain findings of association between LEEP and preterm birth, but LEEP itself may not be an independent risk factor for preterm birth.