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The Bishop Score is a pre-labour cervical assessment tool used to predict the likelihood of successful induction of labour and to determine whether cervical ripening is required before induction. Developed by Edward Bishop in 1964, it quantifies the readiness of the cervix for labour by examining five characteristics on vaginal examination: cervical dilation, effacement (thinning), station of the presenting part relative to the ischial spines, consistency of the cervix, and the position of the cervical os. Each parameter is scored on a sub-scale and the components are summed to produce a total score ranging from 0 to 13. A Bishop score of 8 or above is considered favourable, indicating a cervix that is likely to respond well to oxytocin induction and has outcomes comparable to spontaneous labour. A score below 6 is considered unfavourable, indicating that cervical ripening agents (prostaglandins, Foley catheter balloon, or misoprostol) should be considered before oxytocin infusion. Scores of 6 and 7 are intermediate. The Bishop score is used widely in obstetric units globally to guide decisions about induction of labour at term, post-dates pregnancy, pre-eclampsia, obstetric cholestasis, maternal diabetes, intrauterine growth restriction, and other indications. Its clinical utility is supported by decades of use, though predictive accuracy for successful induction is moderate and factors such as parity, gestational age, indication, and operator experience also influence outcomes.
Bishop Score = Dilation(0-3) + Effacement(0-3) + Station(0-3) + Consistency(0-2) + Position(0-2); Total 0-13; Score ≥8 = Favourable (proceed with oxytocin); Score <6 = Unfavourable (cervical ripening first); 6-7 = Intermediate
- 1Perform a sterile vaginal examination with the patient's informed consent. Assess each of the five cervical parameters in sequence.
- 2Score cervical dilation: 0 = closed; 1 = 1-2 cm; 2 = 3-4 cm; 3 = ≥5 cm.
- 3Score cervical effacement (percentage thinning relative to an uneffaced thick cervix): 0 = 0-30%; 1 = 40-50%; 2 = 60-70%; 3 = ≥80%.
- 4Score fetal station (descent of the presenting part relative to the ischial spines in centimetres): 0 = -3; 1 = -2; 2 = -1/0; 3 = +1/+2.
- 5Score cervical consistency: 0 = firm (like the tip of the nose); 1 = medium (like the earlobe); 2 = soft (like the lips).
- 6Score cervical position: 0 = posterior (os pointing towards the sacrum); 1 = mid; 2 = anterior (os pointing toward the introitus).
- 7Sum all five components. Interpret: ≥8 = favourable, proceed with oxytocin induction; 6-7 = intermediate, clinical judgement required; <6 = unfavourable, initiate cervical ripening with prostaglandins, misoprostol, or mechanical method before oxytocin.
Parous woman with score 10 — likely rapid response to oxytocin; low dose starting regimen appropriate
A score of 10 indicates a cervix primed for labour. Induction with low-dose oxytocin should achieve adequate contractions readily. Continuous CTG monitoring throughout induction is essential.
Options: vaginal prostaglandin E2 (dinoprostone), misoprostol 25 mcg 4-hourly, or Foley catheter balloon
A completely unripe cervix in a nulliparous woman will not respond to oxytocin alone. Cervical ripening over 12-24 hours using prostaglandins or mechanical methods is required to achieve a favourable Bishop score before oxytocin.
Parity and clinical context inform decision — multiparous women often respond to oxytocin at lower Bishop scores
A multiparous woman with a Bishop score of 6 may respond well to a low-dose oxytocin infusion given her cervical response in previous labours. A nulliparous woman with the same score might benefit from one dose of cervical ripening first.
Re-examine 6 hours after prostaglandin insertion; if score ≥6, oxytocin or ARM appropriate
Prostaglandin ripening has successfully transformed an unfavourable cervix to a highly favourable one. Artificial rupture of membranes (ARM) combined with oxytocin is now appropriate to complete the induction.
Pre-induction assessment in all indicated inductions of labour at term and preterm to guide the choice of cervical ripening or direct oxytocin, enabling practitioners to make well-informed quantitative decisions based on validated computational methods and industry-standard approaches
Post-ripening re-assessment after prostaglandin or balloon catheter to determine readiness for oxytocin or ARM, helping analysts produce accurate results that support strategic planning, resource allocation, and performance benchmarking across organizations
Clinical audit: Bishop score at induction onset and time-to-delivery are key metrics in induction audit programmes, allowing professionals to quantify outcomes systematically and compare scenarios using reliable mathematical frameworks and established formulas
Teaching tool for trainee obstetricians and midwives learning to perform and interpret vaginal examination in the obstetric context, supporting data-driven evaluation processes where numerical precision is essential for compliance, reporting, and optimization objectives
Research: Bishop score is routinely recorded in randomised controlled trials comparing induction methods as a baseline covariate affecting outcome, which requires precise quantitative analysis to support evidence-based decisions, strategic resource allocation, and performance optimization across diverse organizational contexts and professional disciplines
Previous Caesarean Section
In women with a previous uterine scar (VBAC candidates), prostaglandins increase the risk of uterine rupture and are contraindicated or used with great caution. Mechanical cervical ripening with a Foley catheter balloon is the preferred method for women with prior caesarean who require induction and have an unfavourable Bishop score. Oxytocin can be used but with lower dose escalation and enhanced uterine activity monitoring.
Multiple Pregnancy
Bishop score applies to the presenting twin in twin pregnancy induction. Induction of twin pregnancy follows similar principles to singleton but with additional complexity from the second twin and different delivery mode discussions. The Bishop score guides the timing and method of induction and is assessed for the presenting twin.
Preterm Induction
When induction is indicated before 37 weeks (e.g., pre-eclampsia, chorioamnionitis, significant IUGR), Bishop score remains relevant but cervical ripening in the preterm cervix may be less predictable. Very preterm inductions may require multiple prostaglandin doses and longer ripening periods. Corticosteroids for fetal lung maturity should be administered before induction below 34 weeks.
Intrauterine Fetal Death
In intrauterine fetal death (IUFD), cervical ripening and induction are required. Mifepristone followed by misoprostol is the preferred protocol in most guidelines for IUFD, particularly at earlier gestations. Bishop score guides the approach but higher-dose misoprostol protocols are used compared to term induction of labour with a live fetus.
| Parameter | Score 0 | Score 1 | Score 2 | Score 3 |
|---|---|---|---|---|
| Dilation (cm) | Closed | 1-2 | 3-4 | ≥5 |
| Effacement (%) | 0-30 | 40-50 | 60-70 | ≥80 |
| Station | -3 | -2 | -1 or 0 | +1 or +2 |
| Consistency | Firm | Medium | Soft | – |
| Position | Posterior | Mid | Anterior | – |
What Bishop Score is considered favourable for induction?
A Bishop score of 8 or above is considered favourable, associated with induction success rates comparable to spontaneous labour. Scores below 6 are unfavourable and warrant cervical ripening. Scores of 6-7 are intermediate — clinical context (parity, indication, gestational age) should inform the decision. Understanding this aspect of bishop score is important for obtaining accurate and meaningful results in both clinical and analytical contexts.
What cervical ripening methods are available?
Pharmacological methods include vaginal prostaglandin E2 (dinoprostone gel or pessary), oral or vaginal misoprostol, and mifepristone (in some protocols). Mechanical methods include the Foley catheter balloon (inserted through the cervical os and inflated with 30-60 mL saline) and double-balloon devices. Mechanical methods have advantages of not requiring CTG monitoring during placement and being suitable for women with prior uterine surgery.
Does parity affect induction success?
Yes, significantly. Parous women (previously delivered vaginally) have higher induction success rates at any given Bishop score than nulliparous women. A multiparous woman may labour effectively with a score of 5-6, while a nulliparous woman with the same score is more likely to require further ripening or caesarean section. Understanding this aspect of bishop score is important for obtaining accurate and meaningful results in both clinical and analytical contexts.
Is the Bishop score used before all inductions?
Yes — vaginal examination with Bishop score should be performed before all inductions of labour to guide the choice of ripening method and predict likely response. It also establishes a baseline to assess progress and cervical change during the induction process. Understanding this aspect of bishop score is important for obtaining accurate and meaningful results in both clinical and analytical contexts.
Can the Bishop score predict caesarean section risk?
A low Bishop score (<6) is associated with higher caesarean section rates during induced labour, particularly in nulliparous women. A systematic review found that women with a Bishop score below 6 who were induced had approximately twice the caesarean section rate compared to those with scores of 6 or above. However, the Bishop score is a moderate rather than strong predictor.
What is the modified Bishop score?
Several modifications of the original Bishop score exist, including the Calder modification which alters the sub-scale ranges. The most significant modification replaces the effacement percentage with cervical length in centimetres: 0 points for length >4 cm; 1 point for 2-4 cm; 2 points for 1-2 cm; 3 points for <1 cm. This modification is used in some centres.
Can ultrasound measurement of cervical length replace the Bishop score?
Transvaginal USS measurement of cervical length is an objective, reproducible alternative to vaginal examination. A cervical length under 25 mm predicts induction success better than the Bishop score in some studies. Many modern protocols combine USS cervical length with clinical Bishop score. Fetal fibronectin (fFN) adds further predictive value. Understanding this aspect of bishop score is important for obtaining accurate and meaningful results in both clinical and analytical contexts.
What is the significance of cervical consistency in the Bishop score?
Cervical consistency reflects the degree of cervical softening (ripening) driven by prostaglandin-mediated collagen remodelling. A firm posterior cervix has not undergone the biochemical changes required for effacement and dilation. Consistency is scored from firm (0) to soft (2), with softening being a prerequisite for subsequent effacement and dilation. Understanding this aspect of bishop score is important for obtaining accurate and meaningful results in both clinical and analytical contexts.
プロのヒント
When assessing the Bishop score, the most prognostically important components are dilation and effacement. A cervix that is 2 cm dilated and 70% effaced will almost always respond to oxytocin regardless of consistency, position, or station — the Bishop score provides useful context, but dilation and effacement are the dominant drivers of induction success.
ご存知でしたか？
Edward Bishop published his cervical scoring system in 1964 based on data from 500 multiparous women undergoing elective induction. He originally intended it only for parous women. The score was subsequently applied to nulliparous women and to clinical induction for medical indications, contexts he had not studied — a testament to how quickly useful clinical tools get generalised beyond their original derivation populations.
参考文献
- ›Bishop EH. Pelvic scoring for elective induction. Obstet Gynecol 1964.
- ›NICE Guideline NG207 — Inducing labour. 2021 (updated 2023).
- ›Crane JM. Factors predicting labour induction success: a critical analysis. Can J Obstet Gynaecol 2006.
- ›Ezebialu IU et al. Methods for assessing pre-induction cervical ripening. Cochrane Review 2015.