Bishop Score
Assessment of cervical readiness for labor induction.
Understanding and Using the Bishop Score in Obstetrics
The Bishop score, developed in 1964 by Dr. Edward Bishop, is the most widely used clinical scoring system in obstetrics to assess cervical ripeness (readiness of the cervix) prior to the artificial induction of labor. This assessment allows the clinician to predict the likelihood of a successful induction leading to a vaginal delivery.
The 5 Components of Pelvic Assessment
The score is based on a precise digital vaginal examination that evaluates five fundamental parameters. Each of these parameters is scored from 0 to 2 or 3, for a maximum total score of 13 points:
- Dilation: Measurement of the opening of the internal cervical os (in centimeters). A cervix that is already open scores higher.
- Effacement: Shortening of the cervical length. A baseline long cervix effaces (shortens and thins) as labor approaches, often expressed as a percentage.
- Station: Position of the fetal presenting part (usually the head) relative to the maternal ischial spines. An engaged head (+1, +2) gets the maximum score.
- Consistency: Changes in the texture of the cervix. A firm cervix (like the tip of a nose) indicates it is not ready, while a soft cervix (like the lips) shows advanced ripening.
- Position: Orientation of the cervical os. Initially posterior, the cervix aligns with the vaginal axis (anterior position) when labor is imminent.
Limitations and Modern Considerations
Although widely used, the Bishop score carries a degree of inter-examiner subjectivity. Today, some studies suggest that transvaginal ultrasound (to measure exact cervical length) could offer an objective complementary assessment. Furthermore, a "modified Bishop score" is sometimes used, replacing effacement with cervical length in centimeters.
Clinical Interpretation and Decision
The interpretation of the score dictates the preferred method of induction:
| Total Score | Cervical Status | Recommendation |
|---|---|---|
| ≤ 5 points | Unfavorable cervix | Cervical ripening method (prostaglandins, balloon catheter) recommended prior to oxytocin infusion. |
| 6 - 8 points | Intermediate cervix | Induction possible, but the success rate remains variable. |
| ≥ 9 points | Favorable cervix | Very high probability of vaginal delivery with amniotomy and/or oxytocin alone. |
References:
1. Bishop EH. Pelvic scoring for elective induction. Obstet Gynecol. 1964 Aug;24:266-8. [PubMed]
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