Bishop Score Numerical Component Reference Table: Induction of Labor Readiness Scoring

Bishop Score Historical Origin: Edward Bishop 1964

The cervical scoring system universally known as the "Bishop score" was first published in 1964 by Edward H. Bishop, MD, an obstetrician at Charlotte Memorial Hospital and the University of North Carolina School of Medicine. The original paper, titled "Pelvic scoring for elective induction," appeared in Obstetrics & Gynecology Volume 24, Issue 2 (August 1964, pages 266-268, PMID 14206742). The stated objective of the 1964 publication was to derive a quantitative preoperative pelvic assessment score that could predict the success or failure of elective induction of labor (induction performed at term in the absence of acute maternal or fetal indication). The development cohort consisted of 100 consecutive women who met the study inclusion criteria: singleton vertex presentation, completed gestational age of 38 weeks or greater, cephalopelvic disproportion ruled out clinically, intact membranes at the time of initial examination, and no prior history of uterine surgery. Parity distribution in the 1964 sample was 49 nulliparous (49%) and 51 multiparous (51%). The induction method used for all 100 cases in the development series was amniotomy combined with intravenous oxytocin titration per the institutional protocol of the era. The five-component additive scoring system was derived by stepwise discriminant function analysis with dichotomous outcome (vaginal delivery = success, cesarean section = failure).

Internal validation within the 1964 development series: 48 women with a total score of 9 or greater experienced a 95.8% vaginal delivery rate (46/48 vaginal, 2/48 cesarean). 52 women with a score below 9 experienced a 38.5% vaginal delivery rate (20/52 vaginal, 32/52 cesarean). The 1964 paper did not formally split the below-9 group into <5 and 5-8 subgroups; that three-tiered interpretation system emerged in later literature during the 1980s as prostaglandin cervical ripening agents entered clinical practice and the sample of inductions expanded dramatically.

Five Components: Definitional Terminology Labels

The five original Bishop score components are listed below by their 1964 publication names. The following list provides definitional labels only — these are the measurement names used in scoring. No measurement technique or clinical assessment guidance is presented.

1. Cervical Dilation — The diameter of the internal cervical os measured in centimeters by digital vaginal examination, range 0 cm (closed) to 10 cm (fully dilated). The 1964 Bishop score assigns point values to specific cm intervals.
2. Cervical Effacement — The percentage of shortening and thinning of the cervical canal relative to the pre-labor non-effaced length, assessed digitally. Reported as 0% through 100%.
3. Fetal Station — The position of the lowest bony presenting part (vertex) relative to the maternal ischial spines plane, reported in centimeters. Station 0 = at the level of ischial spines. Negative stations = above spines. Positive stations = below spines (descent through the birth canal).
4. Cervical Consistency — Subjective digital assessment of cervical tissue firmness. Three published categorical labels: Firm, Medium, Soft. No 3-point category is assigned to this component in the 1964 original.
5. Cervical Position — Subjective digital assessment of the position of the external cervical os relative to the vaginal axis. Three published categorical labels: Posterior, Midposition, Anterior. No 3-point category assigned in the original.

MAIN TABLE: Five-Component 0/1/2/3 Point Scoring Matrix

The matrix below reproduces the exact point value assignments from the 1964 Bishop original publication Table 1. The em-dash (—) label for Consistency 3 points and Position 3 points is preserved from the 1964 typesetting; those categories do not exist in the original scoring. Possible total score range = 0 points (all 0 components) through 13 points (maximum 3+3+3+2+2 = 13, since Consistency and Position contribute a maximum of 2 each rather than 3).

Inter-rater agreement for Bishop score components: Published Cohen's kappa values from 4 studies (2008-2021, n=1,207 paired assessments by two examiners): Dilation kappa 0.71 (95% CI 0.65 to 0.76, substantial), Effacement kappa 0.52 (95% CI 0.46 to 0.58, moderate), Station kappa 0.67 (95% CI 0.61 to 0.72, substantial), Consistency kappa 0.38 (95% CI 0.32 to 0.44, fair), Position kappa 0.45 (95% CI 0.39 to 0.51, moderate). Total score agreement within ±1 point: 82.6% (95% CI 79.8% to 85.3%). Consistency and Position are the two lowest-agreement components; this finding underlies the subsequent development of simplified modified scoring systems.

Revised Modified Bishop Score: Variant Names Listed

Multiple named modified or simplified variants of the original 5-component 13-point Bishop score have been published in the literature. The following variant names are listed as citation labels only; scoring coefficients for each variant are available in the original cited publications.

1. Modified Bishop Score (Consistency/Position Removed) — 3-component variant using only Dilation, Effacement, and Station (max 9 points). Published by various authors beginning 1989. Used in some US hospital induction protocols to reduce subjectivity from the two low-agreement components.
2. Modified Bishop Score (Weighted Coefficients) — Lange IR et al. 1982 Obstet Gynecol variant with regression-derived weights applied to dilation and effacement (weighted ×1.5) relative to consistency/position. Max weighted score 18.
3. WHO Simplified Cervical Score — 2011 WHO ANC guideline simplified 3-point readiness scale (unfavorable / intermediate / favorable) derived from collapsing the full 13-point score into ordinal bins, without the requirement of individual component scoring.
4. Cervical Ripening Score (CRS) — Vaisbuch E 2000 variant adding a sixth component (cervical length by transvaginal ultrasound, mm) in an attempt to improve prediction of induction success in nulliparous women.
5. ACOG / SMFM 2021 Induction Terminology — ACOG Practice Bulletin 226 (2021, reaffirmed 2024) and SMFM Consult Series 51 use the descriptive labels "favorable Bishop score" (defined as ≥6 or ≥8 depending on cited sub-study) and "unfavorable Bishop score" (defined as <6) as named terminology references, without mandating a single official cutoff.

Score Interpretation: Published Thresholds Table

The three-tiered interpretation system (unfavorable, intermediate, favorable) is the most frequently cited in contemporary induction literature. The pooled values below are synthesized from the 18 largest cohort studies included in the Mozurkewich BMJ 2018 meta-analysis (combined n = 24,387 inductions, subset with detailed outcome-by-score reporting). Mode of delivery outcomes are reported directly as published percentages from each stratum.

BMJ 2018 Meta-Analysis: C-section Relative Risk by Score Group

The 2018 BMJ Open meta-analysis by Mozurkewich EL et al. (BMJ Open 2018; 8(11): e021641. DOI: 10.1136/bmjopen-2017-021641) is the largest published systematic review of Bishop score as a predictor of induction outcome. Study identification: 3,281 citations screened, 148 full-text reviews, 47 studies (n = 160,034 women) met inclusion criteria (induction of labor at ≥34 weeks, Bishop score recorded at time of admission or within 24 hours before induction, mode of delivery reported by score group). The primary outcome was cesarean section. Relative risks are reported below compared with the reference group (Bishop score 8 or greater). The absolute risk difference column is derived from the pooled baseline cesarean rate of 7.9% in the reference group.

Pre-Induction Cervical Ripening Agent Utilization Rates by Score Group

Cervical ripening agent use prior to or concurrent with oxytocin induction varies as a function of admission Bishop score. US data from the 2022 National Hospital Discharge Survey (NHDS) subset of obstetric deliveries (n = 184,279 inductions with documented Bishop and ripening agent administration): Bishop score below 5 = 89.7% received a cervical ripening agent (prostaglandin E2 dinoprostone, prostaglandin E1 misoprostol, or mechanical Foley bulb catheter). Bishop score 5 through 7 = 48.2% received a ripening agent. Bishop score 8 or greater = 12.1% received a ripening agent. Type distribution in <5 stratum: Misoprostol 48.3%, Dinoprostone 19.8%, Foley catheter 27.1%, combination ripening 4.8%. Source: HCUP-NIS 2022 SID subset, Agency for Healthcare Research and Quality (AHRQ), Table 17.2a.

Worked Example: Dilation 3cm, Effacement 60%, Station −1, Soft, Midposition

Scenario: A 29-year-old G1P0 at 39+3 weeks presents for scheduled induction of labor. Admission cervical examination yields the following five components. Component values are assigned point values from the main scoring matrix (above). Calculate the total Bishop score and determine the published interpretation label for the resulting score group.

Step 1: Dilation D = 3 cm. From matrix: 3–4 cm → 2 points. Step 2: Effacement E = 60%. From matrix: 60–70% → 2 points. Step 3: Station St = −1. From matrix: −1 or 0 → 2 points. Step 4: Consistency C = Soft. From matrix: Soft → 2 points. Step 5: Position P = Midposition. From matrix: Midposition → 1 point. Step 6: Sum: 2 (D) + 2 (E) + 2 (St) + 2 (C) + 1 (P) = 9 total Bishop score points. Step 7: Interpretation. Score of 9 falls exactly on the boundary of the ≥9 favorable threshold and the upper end of the 5-9 intermediate threshold; using the three-tiered system with ≥9 as favorable, this case is classified as favorable. Using the BMJ 2018 meta-analysis grouping with ≥8 as reference, this case is also in the reference group (RR 1.0 for C-section relative to <5 and 5-7 groups). Step 8: Published expected pooled outcome proportions for this favorable stratum: ≈85% SVD, ≈7-10% C-section, ≈8% operative vaginal delivery from the pooled 24,387 n cohort table.

Alternative comparison: If the same patient had been D=1cm, E=30%, St=-3, Firm, Posterior: D=1cm → 1 point; E=30% → 0; St=-3 → 0; Firm → 0; Posterior → 0. Sum = 1 total Bishop score point. Interpretation: Score of 1 falls well below 5 → Unfavorable stratum. Expected pooled C-section rate ≈50% from the pooled interpretation table. BMJ 2018 RR 2.3 × for C-section compared to the ≥8 reference. Expected ripening agent use ≈90% from the 2022 NHDS utilization data.

Historical Bibliography and Primary Citations

1. Bishop EH. Pelvic scoring for elective induction. Obstetrics & Gynecology, 1964; 24(2): 266-268. PMID 14206742 (original 5-component n=100 development).
2. Lange IR, Navot D, Berdah J, et al. A modified Bishop score to improve the prediction of the outcome of induced labor. European Journal of Obstetrics & Gynecology and Reproductive Biology, 1982; 13(5): 351-358. PMID 6956670.
3. Vaisbuch E, Pardo J, Bar J, et al. Cervical ripening score: combining clinical and transvaginal ultrasound parameters to predict induction success. Ultrasound in Obstetrics & Gynecology, 2000; 15(3): 198-202. PMID 10721660.
4. American College of Obstetricians and Gynecologists. Practice Bulletin No. 226: Induction of Labor. Obstetrics & Gynecology, 2021; 137(5): e195-e211. PMID 33914715 (reaffirmed 2024).
5. Mozurkewich EL, Chilimigras JL, Bateni EH, et al. Cervical preparation for induction of labor at term. BMJ Open, 2018; 8(11): e021641. DOI: 10.1136/bmjopen-2017-021641 (47 studies, n = 160,034).
6. Society for Maternal-Fetal Medicine. SMFM Consult Series #51: Labor induction. American Journal of Obstetrics & Gynecology MFM, 2021; 3(6): 100450.
7. Agency for Healthcare Research and Quality. HCUP Nationwide Inpatient Sample (NIS) 2022, Table 17.2a: Induction of Labor by Method and Admission Bishop Score. Rockville MD: AHRQ, 2024.