Bishop Score Components and Assessment
The Bishop score consists of five cervical and fetal parameters that are assessed through digital vaginal examination: cervical dilation, cervical effacement, cervical consistency (firmness), cervical position, and fetal station. 1
The Five Components
1. Cervical Dilation
- Measured in centimeters (0-10 cm)
- This is the strongest predictor of successful labor induction among all Bishop score components 2
- Scored as:
- 0 points: Closed
- 1 point: 1-2 cm
- 2 points: 3-4 cm
- 3 points: ≥5 cm
2. Cervical Effacement
- Measured as percentage of cervical thinning (0-100%)
- Significant for induction outcome regardless of parity 3
- Scored as:
- 0 points: 0-30%
- 1 point: 40-50%
- 2 points: 60-70%
- 3 points: ≥80%
3. Cervical Consistency (Firmness)
- Assessed by palpation during digital examination
- Has poor prognostic value regardless of parity 3
- Scored as:
- 0 points: Firm
- 1 point: Medium
- 2 points: Soft
4. Cervical Position
- Determined by the orientation of the cervix in the vaginal canal
- Good prognostic factor for induction outcome but less robust association than dilation 1
- Scored as:
- 0 points: Posterior
- 1 point: Mid-position
- 2 points: Anterior
5. Fetal Station
- Position of the presenting fetal part relative to maternal ischial spines (measured in centimeters: -3 to +3)
- Valuable criterion for nulliparous women but has no prognostic value for multiparous women 3
- The only component independently predictive of vaginal delivery within 60 hours in some studies 4
- Scored as:
- 0 points: -3 station
- 1 point: -2 station
- 2 points: -1 or 0 station
- 3 points: +1 or +2 station
Clinical Context
A modified Bishop score <5 defines an unfavorable cervix requiring cervical ripening agents before induction 5. The total score ranges from 0-13 points, with higher scores indicating greater cervical favorability and higher likelihood of successful induction.
Despite criticisms about equal weighting of all five components when cervical dilation appears most predictive, no modifications to the original Bishop score have improved its predictive ability 1, 6. The Bishop score remains the simplest, most cost-effective, and most widely validated method for preinduction cervical assessment 6.