Second-trimester cervical length and outcomes of induction of labor at term

Objective: To evaluate whether second-trimester cervical length (CL) is associated with induction of labor (IOL) outcomes. Methods: Retrospective cohort study of nulliparous singletons undergoing CL screening at 18 0/7-23 6/7 weeks from 1/1/2012 to 12/31/2013. Women induced at term (>= 37 weeks) were included. Primary outcome was vaginal delivery (VD) within 24 h. The effect of CL on outcomes was assessed by incidence across CL quartiles and a receiver operating characteristics (ROC) curve. Odds ratios (OR) were adjusted (aOR) for confounders. Results: Two-hundred-and-sixty-eight women were included. Aside from a difference in incidence of prior cervical surgery between CL quartiles (p < .02), other characteristics were similar. Ninety-two women (35%) had a VD within 24 h (versus a CD or VD >24 h). A longer a CL was associated with a decreased likelihood of a VD within 24 h with aORs of the third and fourth quartiles of 0.35 (0.16-0.75) and 0.43 (0.21-0.90), respectively, compared to the first quartile. A CL >40mm was predictive of not having a VD within 24 h with a sensitivity of 56%, specificity of 58% and a positive predictive value of 72%. Conclusion: A second-trimester CL >40mm is associated with a decreased likelihood of VD within 24 h in an IOL.