COMPARISON OF ULTRASONOGRAPHIC CERVICAL LENGTH AND THE BISHOP’S SCORE IN PREDICTING SUCCESSFUL LABOUR INDUCTION

Abstract

Background: The Bishop’s score is widely used to assess cervical readiness and predict the success of labour induction, drawing on factors such as foetal position, effacement, dilation, and cervical consistency. Higher scores, particularly above 7, are strongly associated with successful vaginal delivery. However, cervical assessment via digital examination can be challenging, especially with a closed cervix, and subjective evaluations are less reliable at lower scores. Transvaginal ultrasound offers a more objective and reproducible method for measuring cervical length, allowing for improved assessment of cervical status, including regions that are difficult to evaluate clinically.

Aim: To investigate the relationship between transvaginal ultrasonographic cervical length measurements and the Bishop’s score in predicting successful labour induction.

Methods: Study group consists of 136 pregnant women attending a tertiary care centre of south India. Transvaginal ultrasound was performed to measure cervical length one day prior to labour induction, using a 6.5 MHz probe with participants in the lithotomy position and an empty bladder. The measurement, performed by a single radiologist, spanned from the internal to the external OS. The Bishop’s score was determined through digital examination, and induction methods were selected based on the score: Foley catheter for scores <3, PGE1 for scores 4–5, and ARM or oxytocin for scores >6. Labour progress and outcomes were systematically recorded.

Results: The study found that a cervical length of 27 mm demonstrated a sensitivity of 84.5% and a specificity of 80.1%, indicating a reasonable balance between these two metrics (AUC = 0.91). Furthermore, participants with a Bishop’s score of 4 exhibited the highest sensitivity at 89% and a specificity of 91%, indicating that this cutoff is both highly sensitive and specific (AUC = 0.95).

Conclusion: The study demonstrates the significant predictive value of both cervical length and Bishop’s scores in assessing the likelihood of successful labour induction, with the Bishop’s score showing greater predictive capability than cervical length. These findings support the integration of these assessments into clinical practice to enhance induction outcomes, optimize resource utilization, and improve maternal and foetal health.