Biochemical and biophysical predictors of the response to the induction of labor in nulliparous postterm pregnancy

Objective: The objective of the study was to evaluate the clinical, sonographic, and hormonal variables that influence the success of labor induction in nulliparous postterm pregnancies. Study Design: Fifty nulliparous women with a single postterm pregnancy receiving a slow-release prostaglandin estradiol pessary were prospectively enrolled, and clinical characteristics were analyzed in relation to success of induction of labor. Clinical, sonographic, and hormonal variables were analyzed by univariate statistical analysis and multivariate logistic regression for the prediction of successful induction.Results: The group of patients delivering within 24 hours differed significantly from the remaining patients by higher Bishop scores, body mass indices, estradiol serum concentrations, estriol to estradiol ratios, and shorter cervices. The combination of cervical length and estriol to estradiol ratio achieved a sensitivity of 100% (95% confidence interval, 71.3–100%) and a specificity of 94.1% (95% confidence interval, 80.3–99.1%).Conclusion: Cervical length and the estriol to estradiol ratio represent good predictive indicators of the response to the induction of labor in postterm pregnancies