Bishop Score vs. ultrasound cervical length in the prediction of cervical ripening success and vaginal delivery in nulliparous women

Abstract

Aim: The aim of this paper was to compare the predictive value of Bishop Score and sonographic measurement of cervical length for predicting cervical ripening success and vaginal delivery in nulliparous women with low Bishop Score.

Methods: A prospective observational study including 77 nulliparous pregnant women at exactly 41 weeks of gestation with a Bishop Score ≤ 5. Cervical measurement was performed by transvaginal ultrasonography and Bishop Score was determined by digital examination. All patients had cervical ripening with Prostaglandins prior to labor induction with oxytocin.

Results: Cervical ripening was successful in 63 patients (81%) and vaginal delivery occurred in 51 women (66.2%). Multiple logistic regression analysis demonstrated cervical length assessed by transvaginal sonography as the only independent predictor of successful cervical ripening and vaginal delivery. The best cut-off point was 34.6 for predicting successful cervical ripening and 32.5 mm for predicting vaginal delivery. The chance of vaginal delivery was 90% when initial cervical length was < 32.5 mm and 50% when cervical length was >32.5 mm.

Conclusion: Compared with the Bishop score, ultrasound cervical length measurement is a better predictor of cervical ripening success and vaginal delivery in nulliparous women at 41 weeks of gestation with an unfavorable cervix.