Prediction of the outcome of labour induction at term by transvaginal ultrasound in supine and upright position

Introduction Aim of this study was to examine the predictive value of cervical length (CL) as measured by transvaginal sonography (TVS) in supine and upright maternal position on the outcome of induction of labour at term, and to compare these measures with the Bishop Score.

Methods TVS and digital examination of the cervix was performed in 73 nulliparous and 34 parous women before induction of labour at term. The Bishop Score and TVS parameters were used for the prediction of a vaginal delivery after labour induction.

Results Logistic regression analysis showed that only the CL in upright position was a significant predictor of the risk of caesarean section (CS) (OR 1.14; 95% CI 1.02;1.27). The area under the curve for the risk of a CS due to failure of progress was higher for the CL, either in supine or upright position, than for the Bishop Score (0.66, 0.68 and 0.46 respectively). Only the Bishop Score correlated significantly with the induction-to-delivery interval. However, when oxytocin and prostaglandin induction were analyzed separately, the latter correlation was not significant anymore.

Conclusion Sonographic CL measurements, especially in upright position, are better indication of the risk of CS after induction of labour than the Bishop Score. The latter correlates better with the duration of labour.