What does a Bishop score indicate?

Bishop Score: Assessment of Cervical Readiness for Labor Induction

The Bishop score is a clinical scoring system that evaluates the readiness of the cervix for labor induction by assessing five components: cervical dilation, effacement, consistency, position, and the station of the presenting part. 1

Components of the Bishop Score

The Bishop score evaluates:

• Cervical dilation: The opening of the cervix measured in centimeters 1
• Cervical effacement: The thinning of the cervix, expressed as a percentage 1
• Cervical consistency: Whether the cervix feels soft or firm 1
• Cervical position: Whether the cervix is anterior (forward), mid-position, or posterior (backward) 1
• Station of the presenting part: The relationship of the fetal presenting part to the ischial spines 1

Clinical Significance and Utility

• Predicts success of labor induction: A higher Bishop score indicates a more favorable cervix and a greater likelihood of successful vaginal delivery 1, 2
• Guides labor management decisions: The score helps determine whether cervical ripening is needed before oxytocin administration 3
• Favorable vs. unfavorable cervix:
  • A favorable Bishop score (traditionally >8 in the original score or >5 in the simplified version) suggests a high probability of successful induction 2
  • An unfavorable score indicates the need for cervical ripening before induction 3

Simplified Bishop Score

• Recent research supports using a simplified Bishop score that includes only dilation, station, and effacement 2
• The simplified score (range 0-9) performs as well as or better than the original score (range 0-13) in predicting successful induction 2
• A simplified Bishop score >5 is considered favorable with a positive predictive value of 87.7% for vaginal delivery 2

Clinical Applications

• Timing of delivery: Helps individualize timing decisions based on the gravida's cervical status 1
• Method of induction: Guides the choice of induction method 1
  • Oxytocin and artificial rupture of membranes are indicated when the Bishop score is favorable 1
  • Cervical ripening agents are recommended when the score is unfavorable 1
• Predicting cesarean delivery risk: Women with a favorable Bishop score after cervical ripening have significantly lower rates of cesarean delivery (RR 0.35,95% CI 0.30-0.40) 3

Comparison with Other Assessment Methods

• While transvaginal ultrasound measurement of cervical length has been proposed as an alternative, evidence regarding its superiority is mixed 4, 5
• Some studies suggest transvaginal ultrasound is a better predictor of successful induction 4
• Other studies indicate the Bishop score remains superior in predicting response to induction 5
• Among the components of the Bishop score, cervical dilation appears to have the strongest association with successful labor 6

Limitations and Considerations

• The Bishop score is subjective and can vary between examiners 6
• Despite its limitations, it remains the most cost-effective and widely used method to assess cervical readiness for induction 6
• The score should be considered alongside other factors such as parity, which independently contributes to the prediction of successful vaginal delivery 4