Prediction of successful induction of labor: comparison of transvaginal ultrasonography and the Bishop score.

OBJECTIVE

To determine whether transvaginal ultrasonography of the cervix before induction of labor is a better predictor of successful induction than the Bishop score.

STUDY DESIGN

Eighty-six consecutive patients scheduled for induction of labor underwent digital cervical examination followed by transvaginal ultrasonography to measure cervical length and to determine the presence of wedging. Patients were induced with either oxytocin or intracervical prostaglandin E2 gel followed by oxytocin when required. The agent for induction was selected on the basis of the digital examination. The primary outcome criteria were successful induction and the duration of labor.

RESULTS

Successful induction and the duration of labor were significantly associated with the Bishop score and cervical length. Cervical wedging was associated only with successful induction. However, in a logistic regression model that included these parameters as independent variables, only the Bishop score and parity were significantly correlated with successful induction and the duration of labor.

CONCLUSIONS

Transvaginal ultrasonographic evaluation of the cervix before induction of labor does not improve the prediction of cervical inducibility obtained by the Bishop score.