[The opening of the internal cervical os predicts cervical ripening better than Bishop's score in nulliparous women at 41 weeks gestation]. / L'ouverture de l'orifice interne du col prédit mieux l'issue de la maturation cervicale que le score de Bishop chez les nullipares à 41 semaines d'aménorrhée.

INTRODUCTION: The objectif was to evaluate ultrasound measurement of the opening of the internal cervical os in the prediction of cervical ripening and to compare it with Bishop's score. METHODS: We conducted a prospective study of 77 nulliparous women admitted to hospital in labor at 41w gestation, with Bishop's Score < 6, over a 10-month period, between July 2012 and April 2013. The measurement of the opening of the internal cervical os was performed using transvaginal ultrasound and Bishop's score was determined by clinical examination. All patients received prostaglandins for cervical ripening. RESULTS: Cervical ripening was successful among 63 patients (81%). Bishop's score and the opening of the internal cervical os were statistically associated with the success or failure of cervical ripening. The success rate of cervical ripening was 100% when the opening of the internal cervical os was equal to or greater than 5 mm (sensitivity: 54%, specificity: 86%). ROC curves showed that the measurement of the internal cervical os was more predictive of cervical ripening than Bishop's score (area under the curve: 0.733 and 0.704 respectively). CONCLUSION: Compared to Bishop's score, echographic measurement of the opening of the internal cervical os is more predictive of the success of cervical ripening in nulliparous women at 41 weeks of pregnancy with an unfavourable cervix.