Hong Life CalculatorsUnderstanding the Bishop score calculator — concept and principle
The Bishop score summarises how ready the cervix is for labour. Obstetricians and midwives use it when planning an induction of labour: a "ripe" cervix makes induction more likely to lead to a vaginal birth, while an "unripe" one often needs cervical ripening first. It was introduced by Edward Bishop in 1964 for planning elective induction and remains the most widely used cervical assessment.
How it is calculated
Five findings from a vaginal examination are scored and added:
- Dilation: 0 cm = 0; 1–2 cm = 1; 3–4 cm = 2; 5 cm or more = 3.
- Effacement: 0–30% = 0; 40–50% = 1; 60–70% = 2; 80% or more = 3.
- Station of the presenting part: −3 = 0; −2 = 1; −1 or 0 = 2; +1 or +2 = 3.
- Consistency: firm = 0; medium = 1; soft = 2.
- Position: posterior = 0; mid = 1; anterior = 2.
The total ranges from 0 to 13. This calculator labels 8 or more favourable, exactly 7 intermediate, and 6 or less unfavourable.
The principle
Before labour the cervix changes in a predictable way: it softens, moves forward, thins out (effaces) and begins to open, while the baby's head descends into the pelvis. Each item captures one part of that process, and adding them gives a single measure of ripeness. A high score means the body has already done much of the preparatory work, so contractions started by induction are more likely to progress.
Worked example
- Inputs: dilation 0 cm (0), effacement 0–30% (0), station −3 (0), firm (0), posterior (0).
- Total = 0 + 0 + 0 + 0 + 0 = 0.
- 0 is 6 or less, so the cervix is unfavourable (ripening may be needed).
How to read the result
- 8 or more: favourable. ACOG notes that with a score above 8, the chance of vaginal birth after induction is similar to that after spontaneous labour.
- 6 or less: unfavourable; cervical ripening with medicines or a mechanical balloon is often considered first.
- 7: an intermediate zone where clinicians weigh other factors.
Previous vaginal births make induction more successful at any score. Some units use a modified Bishop score that replaces effacement with cervical length measured by ultrasound.
Common mistakes
- Treating the score as a prediction of when spontaneous labour will start; it is not designed for that.
- Mixing up station: negative numbers mean the head is still above the ischial spines.
- Comparing scores taken by different examiners as if they were exact; the examination is partly subjective.
Frequently asked questions
What is the highest possible Bishop score?
13.
Does a low score mean I will need a caesarean?
No. Many people with a low score give birth vaginally after cervical ripening.
Can the score change in a day?
Yes. The cervix can change quickly near term, so the score is repeated when needed.
Sources: Bishop EH, Pelvic scoring for elective induction, Obstetrics & Gynecology 1964 · American College of Obstetricians and Gynecologists, Practice Bulletin No. 107: Induction of Labor, 2009