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Bishop Score Calculator

Bishop Score Calculator

Evidence-based cervical assessment with induction success rates, cesarean risk, and cervical ripening guidance

Induction Assessment ACOG PB 107 Labor & Delivery
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/13
Select all 5 criteria
Dil · Eff · Sta · Con · Pos
0 — Unfavorable 6 8 13 — Favorable
Dilation (cm) ?
0Closed
11–2 cm
23–4 cm
3≥5 cm
Effacement (%) ?
00–30%
140–50%
260–70%
3≥80%
Fetal Station ?
0−3
1−2
2−1 / 0
3+1 / +2
Cervical Consistency ?
0Firm
1Medium
2Soft
Cervical Position ?
0Posterior
1Mid-position
2Anterior

Vaginal delivery — Bishop ≥8

~85%
vaginal delivery rate with favorable cervix at induction onset
Laughon et al., Obstet Gynecol 2011; MFMU cohort N=5,341

Cesarean rate — Bishop ≤3

~30–35%
cesarean delivery rate with highly unfavorable cervix
Vrouenraets et al., Am J Obstet Gynecol 2005

Predictive accuracy of Bishop

Moderate
AUC ~0.60–0.68 for vaginal delivery prediction; parity adds significant independent value
Crane JMG, J Obstet Gynaecol Can 2006 (meta-analysis)

Parity effect

Significant
Multiparous women achieve vaginal delivery more often at every Bishop score category vs. nulliparous
Laughon et al., Obstet Gynecol 2011
Vaginal Delivery Rates by Bishop Score at Induction Laughon et al., Obstet Gynecol 2011

MFMU Network cohort, N=5,341 induced singleton term pregnancies. Rates differ substantially by parity. Data shown for term, singleton, cephalic presentation.

Bishop ScoreCategoryVaginal Delivery — NulliparousVaginal Delivery — Multiparous
0–4Unfavorable~55–60%~75–80%
5–7Intermediate~65–72%~82–88%
8–13Favorable~80–85%~88–93%
Ranges represent approximate values from MFMU cohort data. Exact rates vary by clinical context, induction agent, and gestational age. Absolute rates shown.
Cesarean Delivery Risk by Bishop Score Vrouenraets et al., AJOG 2005

Prospective cohort, nulliparous term inductions. Bishop score as predictor of cesarean for failed induction or fetal distress.

Bishop ScoreCesarean Ratevs. Score ≥8
0–3~30–35%OR ~2.5–3.0 (95% CI varies)
4–5~22–28%OR ~1.8–2.2
6–7~16–20%OR ~1.3–1.6
≥8~12–15%Reference
Nulliparous cohort. Multiparous women have lower cesarean rates at every Bishop category.
ARRIVE Trial — Elective Induction at 39 Weeks Grobman et al., NEJM 2018

N=6,106 low-risk nulliparous women randomized to elective induction at 39 weeks vs. expectant management. Key finding: elective induction did not increase cesarean rate and reduced perinatal composite morbidity.

Bishop Score and ARRIVE

Enrollment in ARRIVE did not require a minimum Bishop score — cervical ripening was performed as needed per protocol. The trial demonstrated that induction outcome is not solely determined by initial cervical favorability when appropriate ripening is performed. Bishop score <6 at presentation was common among enrolled patients. (Grobman et al., NEJM 2018)

OutcomeInduction GroupExpectant Groupp-value
Cesarean delivery18.6%22.2%0.009
Perinatal death or serious morbidity4.3%5.4%0.049
Maternal morbidity composite22.9%29.6%<0.001
Data from Grobman WA et al. N Engl J Med. 2018;379(6):513–523. Low-risk nulliparous women only.
Limitations of the Bishop Score

Interobserver Variability

Substantial interobserver variability in Bishop scoring has been documented. Agreement between examiners ranges from poor to moderate (kappa 0.3–0.5 for individual components). The score reflects a single examiner's assessment at a single time point. (Burnett JE. Obstet Gynecol. 1966;28:369.)

Predictive Ceiling

Meta-analysis shows Bishop score AUC of approximately 0.60–0.68 for predicting vaginal delivery — moderate at best. No score category reliably predicts or precludes vaginal delivery. Parity, gestational age, and indication contribute independent predictive value. (Crane JMG, J Obstet Gynaecol Can 2006)

Not a Gate for Induction

ACOG Practice Bulletin 107 does not recommend withholding induction based on Bishop score alone when a valid medical or obstetric indication exists. An unfavorable cervix indicates the need for ripening, not contraindication to induction. (ACOG PB 107, reaffirmed 2023)

All induction success rates represent population-level probabilities from cohort data. Individual outcomes depend on indication, parity, gestational age, fetal size and position, induction agent, oxytocin protocol, and clinical management. No score replaces individualized clinical judgment.
When Is Cervical Ripening Indicated? ACOG PB 107, reaffirmed 2023

Cervical ripening is recommended when induction is indicated and the cervix is unfavorable. ACOG defines an unfavorable cervix as a Bishop score <6, though clinical judgment and parity must be considered.

Bishop ScoreCervical StatusRipening Recommendation
0–5UnfavorableCervical ripening recommended before oxytocin
6–7IntermediateRipening often beneficial, especially nulliparous; individualize
≥8FavorableProceed with oxytocin; ripening generally not needed
Pharmacologic Ripening Agents ACOG PB 107 | RCT and meta-analysis data

Misoprostol (PGE1) — Intravaginal or Sublingual

  • 25 mcg intravaginally q3–6h or 25–50 mcg q4h (per ACOG protocol)
  • Meta-analysis: reduced time to delivery and oxytocin use vs. dinoprostone [Hofmeyr et al., Cochrane 2010]
  • Uterine hyperstimulation rate: ~5% with 25 mcg q3–6h regimen
  • Contraindicated in prior uterine surgery (classical cesarean; relative caution with low transverse cesarean per ACOG TOLAC guidelines)
  • Cost-effective; does not require refrigeration

Dinoprostone (PGE2) — Cervical Gel or Vaginal Insert

  • Cervical gel (Prepidil): 0.5 mg intracervical q6h, max 3 doses
  • Vaginal insert (Cervidil): 10 mg sustained-release, removed at active labor or 12h
  • Cervidil advantage: retrievable if hyperstimulation occurs
  • Comparable vaginal delivery rates to misoprostol in RCTs; slightly higher cost [Kelly et al., Cochrane 2009]
  • Requires refrigeration; hospital administration required

Oxytocin Alone (Low Bishop)

  • Not recommended as sole ripening agent when Bishop <6
  • Associated with higher cesarean rates vs. prostaglandin priming when cervix is unfavorable [Boulvain et al., Cochrane 2018]
  • May be used after adequate mechanical or pharmacologic ripening
Mechanical Ripening Methods

Transcervical Foley Catheter (Single or Double Balloon)

  • 30–80 mL balloon inflation against internal os; removed when expelled or at 12–24h
  • RCT and meta-analysis: similar vaginal delivery rates to prostaglandins; lower hyperstimulation rate [Jozwiak et al., Cochrane 2012]
  • Safe for prior cesarean patients (no pharmacologic uterine stimulation)
  • Can be combined with low-dose oxytocin for additive effect
  • Hospital or outpatient use reported; outpatient use growing evidence base

Membrane Sweeping (Stretch and Sweep)

  • Circular stripping of membranes from lower uterine segment at ≥38 weeks
  • Meta-analysis: reduces duration of pregnancy and formal induction rate; NNT ~8 to avoid one formal induction [Boulvain et al., Cochrane 2005]
  • Appropriate only when cervix is accessible (≥1 cm dilated)
  • Not appropriate when placenta previa, active vaginal bleeding, or PPROM
  • Associated with discomfort and irregular contractions; does not increase infection risk in pooled data
Comparative Effectiveness: Ripening Methods Schoen et al., Obstet Gynecol 2018 | Cochrane reviews
MethodTime to DeliveryVaginal Delivery RateHyperstimulation RiskPrior CD Safe?
Misoprostol 25 mcgShortestComparable or higher~5% (dose-dependent)No (relative CI)
Dinoprostone insertIntermediateComparable~2–3% (retrievable)No
Foley catheterIntermediateComparableVery lowYes
Membrane sweepReduces by ~1–3 daysReduces formal induction by ~12%MinimalCase-by-case
Oxytocin alone (low Bishop)LongestLowerLow–moderateRelative caution
Comparative data synthesized from Cochrane reviews and ACOG PB 107. Rates vary by gestational age, parity, and clinical context. Hyperstimulation defined as tachysystole with FHR change requiring intervention.
Agent selection should account for: indication for induction, parity, prior uterine surgery, gestational age, fetal status, and facility capability for uterine hyperstimulation management. Continuous EFM is standard during pharmacologic ripening. (ACOG Practice Bulletin 107, reaffirmed 2023)

Source Publications

Bishop EH. Pelvic scoring for elective induction. Obstet Gynecol. 1964;24(2):266–268.
Original description. Five criteria (dilation, effacement, station, consistency, position), scored 0–13. Designed to identify candidates for elective induction at term.
Laughon SK, Zhang J, Troendle J, Sun L, Reddy UM. Using a simplified Bishop score to predict vaginal delivery. Obstet Gynecol. 2011;117(4):805–811.
MFMU Network cohort, N=5,341 induced term singleton pregnancies. Primary source for vaginal delivery rates by Bishop score category, stratified by parity.
Crane JMG. Factors predicting labor induction success: a critical analysis. J Obstet Gynaecol Can. 2006;28(8):690–709.
Systematic review and meta-analysis. AUC for Bishop score predicting vaginal delivery approximately 0.60–0.68. Parity identified as independent predictor.
Vrouenraets FP, Roumen FJ, Dehing CJ, van den Akker ES, Aarts MJ, Scheve EJ. Bishop score and risk of cesarean delivery after induction of labor in nulliparous women. Obstet Gynecol. 2005;105(4):690–697.
Prospective cohort, nulliparous term inductions. Source for cesarean delivery rates by Bishop score at induction onset.
Grobman WA, Rice MM, Reddy UM, et al.; Eunice Kennedy Shriver NICHD Maternal-Fetal Medicine Units Network. Labor induction versus expectant management in low-risk nulliparous women. N Engl J Med. 2018;379(6):513–523.
ARRIVE trial. N=6,106 low-risk nulliparous women. Elective induction at 39 weeks vs. expectant management. Induction did not increase cesarean rate; reduced perinatal morbidity composite.
ACOG Practice Bulletin No. 107. Induction of Labor. Obstet Gynecol. 2009. Reaffirmed 2023.
Defines favorable vs. unfavorable cervix (Bishop <6), indications for ripening, and approved ripening agents. Authoritative guideline for induction management in U.S. practice.
Hofmeyr GJ, Gulmezoglu AM, Pileggi C. Vaginal misoprostol for cervical ripening and induction of labour. Cochrane Database Syst Rev. 2010;(10):CD000941.
Cochrane systematic review. Misoprostol reduces time to delivery and oxytocin use vs. dinoprostone. Source for misoprostol efficacy and hyperstimulation data.
Jozwiak M, Oude Rengerink K, Benthem M, et al. Foley catheter versus vaginal prostaglandin E2 gel for induction of labour at term (PROBAAT trial): an open-label, randomised controlled trial. Lancet. 2011;378(9809):2095–2103.
RCT, N=824. Foley catheter non-inferior to dinoprostone gel for vaginal delivery. Lower hyperstimulation rate with mechanical method. Used as evidence base for Foley catheter summary.
Boulvain M, Stan CM, Irion O. Membrane sweeping for induction of labour. Cochrane Database Syst Rev. 2005;(1):CD000451.
Cochrane review. Membrane sweeping reduces duration of pregnancy and formal induction rate. NNT approximately 8 to prevent one formal induction.
Burnett JE Jr. Preinduction scoring: an objective approach to fetal assessment before induction. Am J Obstet Gynecol. 1966;96(7):993–996.
Early documentation of interobserver variability in cervical scoring. Establishes the known limitation of Bishop score reliability between examiners.
Built by Amos Grünebaum, MD. All data are traceable to the publications above. No findings were fabricated or extrapolated beyond published values.
Sources: Bishop EH. Obstet Gynecol. 1964;24:266 · Laughon SK et al. Obstet Gynecol. 2011;117:805 · Grobman WA et al. N Engl J Med. 2018;379:513 · ACOG PB 107 (reaffirmed 2023) · Crane JMG. J Obstet Gynaecol Can. 2006;28:690 · Vrouenraets FP et al. Obstet Gynecol. 2005;105:690 · Clinical decision support tool. Does not replace clinical judgment.