About

The Bishop Score is a pre-labor scoring system developed by Dr. Edward Bishop in 1964 to quantify cervical readiness for induction of labor. It assigns ordinal values (0 to 2 or 3) across five parameters: cervical dilation, effacement, fetal station, cervical consistency, and cervical position. The maximum composite score is 13. A score ≤ 5 indicates an unfavorable cervix where induction carries higher risk of cesarean delivery. A score ≥ 8 indicates a favorable cervix with a high probability of successful vaginal delivery following induction, comparable to spontaneous labor outcomes.

Miscalculation or failure to assess cervical favorability before induction can lead to prolonged labor, failed induction, and emergency cesarean section. This tool implements the original Bishop criteria without modification. It does not account for parity-adjusted variants or the use of cervical ripening agents such as prostaglandins or mechanical dilators. Clinical judgment remains essential. Pro tip: document the Bishop Score at multiple time points during cervical ripening to track progression objectively.

Formulas

The Bishop Score is a simple additive index of five cervical and fetal station parameters:

B = D + E + S + C + P

Where B = total Bishop Score (0 - 13), D = dilation score (0 - 3), E = effacement score (0 - 3), S = station score (0 - 3), C = consistency score (0 - 2), and P = position score (0 - 2).

The interpretation follows a piecewise classification:

{

Unfavorable if B ≤ 5Intermediate if 6 ≤ B ≤ 7Favorable if B ≥ 8

Reference Data

Parameter	0 Points	1 Point	2 Points	3 Points
Dilation (cm)	Closed	1 - 2	3 - 4	≥ 5
Effacement (%)	0 - 30	40 - 50	60 - 70	≥ 80
Station	−3	−2	−1, 0	+1, +2
Consistency	Firm	Medium	Soft	-
Position	Posterior	Mid-position	Anterior	-
Interpretation Thresholds
Total Score	≤ 5 → Unfavorable cervix (consider cervical ripening before induction)
Total Score	6 - 7 → Intermediate (variable induction success)
Total Score	≥ 8 → Favorable cervix (high probability of successful induction)
Clinical Context
Nulliparous	Induction success rate with Bishop ≥ 8: approximately 95%
Multiparous	Favorable outcomes often seen at Bishop ≥ 6
Failed Induction Risk	Bishop ≤ 5 carries 2 - 3× higher cesarean risk vs. Bishop ≥ 8
Prostaglandin Ripening	Typically indicated when Bishop < 6
Mechanical Ripening	Foley catheter considered when Bishop ≤ 5
Oxytocin Alone	Generally appropriate when Bishop ≥ 8
Spontaneous Labor	Likely within 1 week if Bishop ≥ 8

Frequently Asked Questions

A Bishop Score ≤ 5 indicates an unfavorable cervix. ACOG guidelines recommend cervical ripening with prostaglandins (e.g., misoprostol, dinoprostone) or mechanical methods (Foley catheter) before initiating oxytocin in these cases. Attempting induction without ripening at a score ≤ 5 significantly increases cesarean delivery risk.

Multiparous women generally achieve successful induction at lower Bishop Scores than nulliparous women. Some clinicians consider a score of 6 favorable for multiparous patients. The original Bishop criteria did not adjust for parity; modified versions exist but lack universal adoption. This calculator uses the unmodified original scoring system.

A Bishop Score ≥ 8 at term correlates with a high probability of spontaneous labor within approximately 1 week. However, the score was designed to predict induction success rather than spontaneous labor timing. Its positive predictive value for spontaneous onset is moderate and should not replace gestational age-based management.

Fetal fibronectin (fFN) and transvaginal cervical length measurement provide independent predictive information about preterm labor risk. For term induction decisions, the Bishop Score remains the primary clinical assessment. Some studies suggest combining Bishop Score with cervical length improves induction outcome prediction, but no composite scoring system has been universally adopted.

The Bishop Score relies on subjective digital cervical examination, introducing inter-observer variability. Consistency and position assessments are particularly subjective. The score does not account for uterine activity, membrane status, or fetal weight. It was validated in the 1960s on a specific population and may not generalize perfectly to all demographics. Objective measurement via ultrasound cervical length has been proposed as a supplement but does not replace the Bishop Score in routine practice.

Standard practice reassesses the Bishop Score every 4 to 6 hours during prostaglandin ripening and prior to initiating oxytocin. Serial assessment allows clinicians to identify progression and determine when the cervix has become favorable enough (typically Bishop ≥ 6) to proceed with amniotomy and oxytocin augmentation.