The association between cervical dysplasia, a short cervix, and preterm birth

OBJECTIVE: We sought to determine whether cervical dysplasia in the absence of an excisional procedure is associated with an increased risk of preterm birth (PTB) and whether that risk is independent of the presence of a short cervix. STUDY DESIGN: This is a cohort study including women with a singleton pregnancy who underwent routine cervical length assessment between 18-23 6/7 weeks of gestation, stratified by cervical dysplasia (ie, no prior dysplasia, prior dysplasia but no excisional procedure, or prior excisional procedure). The frequency of a short cervix (<= 2.5 cm) and PTB were compared between groups and multivariable analyses were performed to identify whether: (1) dysplasia alone or a prior excisional procedure was associated with PTB; and (2) whether these factors remained independently associated with PTB after adjusting for the presence of a short cervix. RESULTS: Of the 18,528 women who met inclusion criteria, 3023 (16.3%) had prior dysplasia alone and 1356 (7.3%) had a prior excisional procedure. The frequency of a short cervix for women without dysplasia, with prior dysplasia alone, or with a prior excisional procedure was 0.8%, 1.0%, and 2.2%, respectively (P <.001). The frequency of PTB, respectively, was 6.4%, 6.5%, and 8.4% (P <.001). After adjusting for potential confounding factors, prior excisional procedure but not prior dysplasia alone was associated with PTB. CONCLUSION: Having a prior cervical excisional procedure but not dysplasia alone is associated with an increased risk of PTB. This association is independent of the presence of a short cervix.