Association between second-trimester cervical length and primary cesarean delivery

OBJECTIVE: To evaluate whether an increased ultrasonographic cervical length in the second trimester is associated with an increased frequency of cesarean delivery. METHODS: This is a retrospective cohort study of nulliparous women with a singleton pregnancy who underwent routine cervical length screening between 16 and 24 weeks of gestation and labored after 34 weeks of gestation at a single tertiary care hospital. Women were grouped by cervical length quartile, and the association between cervical length quartile and cesarean delivery was determined in both univariable and multivariable analyses. RESULTS: For every additional centimeter of cervical length, the odds of cesarean delivery increased by 20.3%. Similarly, the frequency of cesarean delivery increased with increasing second-trimester cervical length quartiles (17.4%, 22.3%, 21.8%, 27.7%; P,.001). This association persisted in multivariable analyses that included gestational age at delivery and induction of labor. This increased risk of cesarean delivery was primarily the result of women with arrest disorders in the first stage of labor (P,.001). CONCLUSION: Increased second-trimester cervical length quartile is associated with an increased frequency of primary cesarean delivery in nulliparous women.