Bishop Score Calculator
Assess cervical favourability before induction of labour. The Bishop Score estimates the likelihood of a successful vaginal delivery following induction, guiding decisions on cervical ripening and induction method.
Calculate Bishop Score
Select the findings from your cervical examination to calculate the Bishop Score. All five parameters are assessed by digital vaginal examination prior to planned induction of labour.
The Bishop Score is a screening tool to estimate cervical readiness — it does not predict the mode of delivery with certainty. A low score suggests that cervical ripening may improve the chance of successful induction, but clinical judgement should guide all management decisions.
Understanding the Bishop Score
The Bishop Score was introduced by Edward Bishop in 1964 as a systematic method for evaluating cervical readiness before elective induction of labour. It remains the most widely used pre-induction assessment tool in obstetric practice worldwide.
The score quantifies five characteristics of the cervix and the fetal presenting part, all assessed by digital vaginal examination. Each parameter reflects physiological changes that occur as the cervix transitions from a firm, closed, posterior structure to a soft, dilated, anterior one — the process known as cervical ripening.
Scoring Formula
Bishop Score = Dilation (0–3) + Effacement (0–3) + Station (0–3) + Consistency (0–2) + Position (0–2)
Range: 0–13 points
Higher scores indicate a more favourable cervix and greater likelihood of successful induction.
Worked Example
A nulliparous woman at 41 weeks:
Dilation 1–2 cm = 1
Effacement 60% = 2
Station −2 = 1
Consistency medium = 1
Position mid = 1
Total = 6 (intermediate — consider ripening)
Key distinction: The Bishop Score estimates the likelihood of successful vaginal delivery after induction — it does not predict whether induction itself is indicated. The decision to induce is based on maternal and fetal indications, while the Bishop Score guides the method of induction.
Score Interpretation & Cervical Favourability
The total Bishop Score is used to categorise the cervix as favourable, intermediate, or unfavourable, which directly informs the approach to induction of labour.
| Bishop Score | Cervical Status | Induction Approach | Vaginal Delivery Likelihood |
|---|---|---|---|
| 0–5 | Unfavourable | Cervical ripening recommended before oxytocin | Lower — similar to spontaneous labour rate |
| 6–7 | Intermediate | Cervical ripening may be beneficial; consider prostaglandins or mechanical methods | Moderate |
| 8–13 | Favourable | Proceed with amniotomy ± oxytocin; ripening typically not required | High — comparable to spontaneous labour |
Some sources use a threshold of ≥6 as favourable (particularly in multiparous women), while others use ≥8. In practice, the most critical distinction is between scores ≤5 (unfavourable — cervical ripening needed) and ≥8 (favourable — direct induction with oxytocin is reasonable). Scores of 6–7 require clinical judgement based on parity, indication urgency, and institutional protocols.
Cervical Ripening Methods & Induction Approaches
When the Bishop Score indicates an unfavourable cervix, cervical ripening before oxytocin augmentation is associated with improved outcomes. Several methods are available, and the choice depends on clinical context, contraindications, and local protocols.
Dinoprostone is available as a vaginal gel (Prostin E2, 1–2 mg) or a controlled-release vaginal insert (Cervidil/Propess, 10 mg over 12–24 hours). It acts by softening the cervical collagen matrix and stimulating myometrial contractions. The insert has the advantage of being removable if hyperstimulation occurs.
Contraindications include prior caesarean section or uterine surgery (relative — varies by guideline), active asthma, and glaucoma. Continuous fetal monitoring is recommended for 30–60 minutes after insertion and when using the insert. The main risk is uterine tachysystole, occurring in approximately 1–5% of cases with the gel and up to 17% with the insert (though the insert can be removed promptly).
Misoprostol can be administered orally (25–50 µg every 4 hours) or vaginally (25 µg every 4–6 hours). It is inexpensive, thermostable, and effective for cervical ripening. Oral low-dose misoprostol (25 µg) has emerged as a preferred regimen in several international guidelines due to a favourable balance of efficacy and safety.
It is generally contraindicated in women with a prior uterine scar due to an increased risk of uterine rupture. Compared with dinoprostone, misoprostol may be associated with a higher rate of tachysystole, but overall maternal and neonatal outcomes are comparable when low-dose regimens are used. Fetal monitoring protocols should follow institutional guidelines.
A Foley catheter (typically 16–18 Fr with 30–60 mL balloon) or a purpose-built double-balloon catheter (e.g., Cook Cervical Ripening Balloon) is inserted through the cervical os. Mechanical dilation occurs through direct pressure and local prostaglandin release. The catheter typically falls out when the cervix reaches 3–4 cm.
Mechanical methods are the preferred option when prostaglandins are contraindicated — particularly in women with a prior caesarean delivery. They carry a lower risk of uterine tachysystole compared with pharmacological methods. They can also be used in combination with low-dose misoprostol in some protocols, which has been shown in recent evidence to reduce time to delivery compared with either method alone.
When the cervix is favourable (Bishop Score ≥8), amniotomy (artificial rupture of membranes) combined with oxytocin infusion is the standard approach for induction. Amniotomy allows assessment of the liquor, application of a fetal scalp electrode if needed, and can accelerate the onset of labour.
Amniotomy requires the presenting part to be sufficiently engaged to minimise the risk of cord prolapse. Oxytocin should be titrated according to hospital protocol, typically starting at 1–2 mU/min and increasing every 30 minutes. Continuous electronic fetal monitoring is required during oxytocin infusion. In some protocols, amniotomy alone is performed first, with oxytocin added after 2 hours if contractions have not become established.
Dilation is the single most predictive component of the Bishop Score. A cervix that is already 3+ cm dilated is strongly associated with successful induction regardless of the other parameters.
Effacement reflects cervical shortening and thinning. In nulliparous women, effacement typically precedes significant dilation. A fully effaced cervix (≥80%) indicates advanced ripening.
Station describes the level of the fetal presenting part relative to the ischial spines. A lower station (0 or below, i.e., engaged) is associated with more successful induction but is also the component with the highest inter-observer variability.
Consistency changes from firm (like the tip of the nose) to soft (like lips) as ripening progresses, reflecting collagen degradation and increased water content. This change is mediated by prostaglandins, matrix metalloproteinases, and inflammatory mediators.
Position shifts from posterior to anterior as ripening occurs, aligning the cervical os with the vaginal axis, which facilitates presentation of the fetal head to the cervix.
When the Bishop Score is ≤5, begin with cervical ripening (prostaglandins or mechanical methods). When the score is ≥8, proceed directly to amniotomy ± oxytocin. For scores of 6–7, consider parity, urgency, and local protocols to determine whether ripening or direct induction is most appropriate.
Special Populations & Considerations
The Bishop Score was originally validated in a predominantly multiparous population. Its predictive accuracy varies across different clinical scenarios, and certain populations require specific consideration when interpreting the score and selecting an induction method.
Cervical length measurement by transvaginal ultrasound has been studied as an adjunct or alternative to the Bishop Score. A cervical length <25 mm is associated with favourable induction outcomes. Some centres use ultrasound cervical length when the digital examination is difficult or when a more objective measurement is desired, but it has not replaced the Bishop Score in routine practice.
Pre-Induction Assessment Workflow
A structured approach to pre-induction assessment ensures that all relevant clinical factors are considered alongside the Bishop Score.
Before assessing cervical readiness, confirm that the indication for induction is appropriate and that the benefits of delivery outweigh the risks of continuing the pregnancy. Common indications include post-dates pregnancy (≥41 weeks), pre-eclampsia or gestational hypertension, gestational diabetes with poor control, prelabour rupture of membranes at term, fetal growth restriction, and oligohydramnios.
Review the ARRIVE trial evidence for elective induction at 39 weeks in low-risk nulliparous women if relevant. Document the indication clearly and discuss with the patient.
Review for absolute contraindications to induction: placenta praevia, vasa praevia, transverse lie, active genital herpes, cord prolapse, and prior classical or T-incision caesarean section. Relative contraindications include prior low-transverse caesarean (requires careful method selection), grand multiparity, and overdistended uterus.
If prostaglandin use is planned, confirm the absence of contraindications specific to prostaglandins (asthma, glaucoma, prior uterine surgery depending on local policy).
Perform a digital vaginal examination and systematically assess all five Bishop Score components: dilation, effacement, station, consistency, and position. Document each parameter individually as well as the total score. The examination should ideally be performed in a setting where induction can commence if the cervix is found to be favourable.
Consider transvaginal ultrasound for cervical length if the digital examination is limited or equivocal.
Bishop Score ≤5 (unfavourable): Begin cervical ripening — prostaglandin E₂ (gel or insert), oral misoprostol, or Foley catheter. Choice depends on uterine scar status, patient preference, and local protocol.
Bishop Score 6–7 (intermediate): Clinical judgement required — consider ripening (particularly in nulliparas) or proceed with amniotomy ± oxytocin if circumstances favour.
Bishop Score ≥8 (favourable): Proceed directly with amniotomy ± oxytocin infusion. Cervical ripening is typically unnecessary.
Common Pitfalls & Limitations
The Bishop Score relies entirely on subjective digital assessment, and inter-observer agreement is only moderate. Station and effacement show the highest variability between examiners, while dilation tends to be the most reproducible component. Two clinicians examining the same patient may arrive at different total scores, particularly for intermediate values.
This variability means that a single Bishop Score assessment should not be treated as a precise measurement. When the score falls in the intermediate range (6–7), the clinical context and parity should carry significant weight in decision-making.
While a favourable Bishop Score is associated with higher rates of vaginal delivery, the score’s overall predictive accuracy for induction outcome is modest. Many women with low Bishop Scores achieve successful vaginal delivery after appropriate cervical ripening, and some women with favourable scores still require caesarean delivery. The score is better at predicting the need for cervical ripening than the ultimate mode of delivery.
Individual components — particularly cervical dilation — may be more predictive than the total score. A cervix that is 3 cm dilated but posterior and firm (total score 5) may respond differently to induction than a closed, soft, anterior cervix (also total score 5).
Parity is not included in the original Bishop Score, yet it is one of the strongest independent predictors of successful induction. A multiparous woman with a Bishop Score of 5 has a significantly higher probability of vaginal delivery than a nulliparous woman with the same score. Failing to account for parity when making induction decisions is a common error that may lead to inappropriate method selection.
Some modified scoring systems add points for parity or adjust thresholds based on parity. Even when using the standard score, clinicians should mentally adjust their interpretation based on the patient’s obstetric history.
The Bishop Score was designed to predict the likelihood of successful induction, not to determine whether induction is indicated. A low Bishop Score is not a reason to defer medically indicated induction — it is a reason to use cervical ripening before oxytocin. Delaying induction solely because the cervix is unfavourable can lead to adverse maternal or fetal outcomes when the indication is time-sensitive.
The decision to induce should be based on clinical indication and gestational age, while the Bishop Score guides how to induce (ripening vs. direct oxytocin).
Several modifications to the original Bishop Score have been proposed, including simplified versions that omit cervical position and consistency (retaining only dilation, effacement, and station). Some institutions use these simplified scores, which may lead to confusion when comparing scores across centres or between studies. Always clarify which version of the score is being used in documentation and communication.
The simplified Bishop Score (0–10) has been shown to have comparable predictive accuracy to the full score in some studies, but institutional protocols may mandate the original 5-component version.
Quick Reference Summary
(5 components)
| Parameter | 0 Points | 1 Point | 2 Points | 3 Points |
|---|---|---|---|---|
| Dilation | Closed | 1–2 cm | 3–4 cm | ≥ 5 cm |
| Effacement | 0–30% | 40–50% | 60–70% | ≥ 80% |
| Station | −3 | −2 | −1, 0 | +1, +2 |
| Consistency | Firm | Medium | Soft | — |
| Position | Posterior | Mid-position | Anterior | — |
The Golden Rule: The Bishop Score tells you how to induce, not whether to induce. A low score is an indication for cervical ripening — it is not a contraindication to induction when a valid clinical indication exists.
Disclaimer & References
For Educational Purposes Only. This calculator and the accompanying clinical information are intended as educational tools for healthcare professionals. They do not replace clinical judgement. Results should be interpreted in the full clinical context. Lab reference ranges vary by institution — verify with your own laboratory. Drug dosages should be confirmed against current prescribing information.
References
- Bishop EH. Pelvic scoring for elective induction. Obstetrics & Gynecology. 1964;24(2):266–268. DOI: 10.1097/00006250-196408000-00018
- Kolkman DGE, Verhoeven CJM, Brinkhorst SJ, et al. The Bishop score as a predictor of labor induction success: a systematic review. American Journal of Perinatology. 2013;30(8):625–630. DOI: 10.1055/s-0032-1331024
- Laughon SK, Zhang J, Troendle J, Sun L, Reddy UM. Using a simplified Bishop score to predict vaginal delivery. Obstetrics & Gynecology. 2011;117(4):805–811. DOI: 10.1097/AOG.0b013e3182114ad2
- ACOG Practice Bulletin No. 107. Induction of labor. Obstetrics & Gynecology. 2009;114(2 Pt 1):386–397. DOI: 10.1097/AOG.0b013e3181b48ef5
- National Institute for Health and Care Excellence (NICE). Inducing labour. NICE guideline [NG207]. 2021. Available at: nice.org.uk/guidance/ng207
- Grobman WA, Rice MM, Reddy UM, et al. Labor induction versus expectant management in low-risk nulliparous women (ARRIVE trial). New England Journal of Medicine. 2018;379(6):513–523. DOI: 10.1056/NEJMoa1800566
- Alfirevic Z, Aflaifel N, Weeks A. Oral misoprostol for induction of labour. Cochrane Database of Systematic Reviews. 2014;(6):CD001338. DOI: 10.1002/14651858.CD001338.pub3
- Jozwiak M, Bloemenkamp KWM, Kelly AJ, et al. Mechanical methods for induction of labour. Cochrane Database of Systematic Reviews. 2012;(3):CD001233. DOI: 10.1002/14651858.CD001233.pub2
- Baños N, Migliorelli F, Posadas E, Ferreri J, Palacio M. Definition of failed induction of labor and its relevance for clinical practice: a systematic review. Acta Obstetricia et Gynecologica Scandinavica. 2015;94(10):1064–1073. DOI: 10.1111/aogs.12685