A way to lend objectivity to Bishop score

Summary

The aim of this study was to explore the possibility of utilising pre-induction cervical length assessment by trans-vaginal ultrasound to improve the predictive value of the Bishop score. The idea of this paper has evolved following our prospective study, which was designed to compare the pre-induction objective assessment of the cervix by ultrasound with the subjective one by Bishop Score. The Bishop scores of the 104 women included in the study were modified by replacing the digital assessment of the cervical length by ultrasound cervical length measurements. There was a significant statistical difference (p < 0.0001) between the median of the original and the modified Bishop scores. The original Bishop score showed insignificant association (p > 0.05) with the induction-delivery interval (IDI) and the mode of delivery while the modified score showed a significant association (r = 0.31, p < 0.05) with mode of delivery and a highly significant one (r = 0.55, p < 0.0001) with the IDI. The receiver operating characteristic curve showed that the optimised cut-off value for prediction of vaginal delivery was >5 for the original Bishop Score and >3 for the modified one. At those optimised cut-off values, the original Bishop Score predicted vaginal delivery with a sensitivity of 23% (95% CI; 14.6%, 33.2%) and specificity of 88.2% (95% CI; 63.5%, 98.5% while the modified Bishop score predicted vaginal delivery with a sensitivity of 62% [95%; CI 51 – 72.3] and specificity of 82% [95%; CI 56.6 – 96]). In conclusion, the modified Bishop score is better than the original one in predicting the IDI and the success of induction of labour. The sensitivity of the Bishop score in predicting the rate of vaginal delivery has been improved significantly following the modification.