What is the Bishop Score?
The Bishop score is a standardized scoring system that evaluates maternal and fetal factors to predict the success of labour induction. Developed in 1964, it assigns points across five clinical observations to generate a single numerical score ranging from 0 to 13.
A higher Bishop score indicates greater readiness for labour and better prospects for vaginal delivery following induction. Conversely, a lower score suggests the cervix is unfavourable for induction, making spontaneous labour more likely to be successful or indicating that cervical ripening may be necessary before attempting induction.
The five parameters assessed are:
- Cervical dilation — the degree to which the cervix has opened, measured in centimetres
- Cervical effacement — the thinning and shortening of the cervix, expressed as a percentage
- Cervical consistency — whether the cervix feels firm, moderately firm, or soft during examination
- Fetal station — how far the baby's head has descended into the pelvis relative to the ischial spines
- Fetal position — the direction the baby's head is facing (anterior or posterior)
Bishop Score Calculation
Each of the five parameters receives a point value based on clinical findings. The Bishop score is simply the sum of these five individual component scores.
Bishop Score = Cervical Dilation Points + Cervical Effacement Points + Cervical Consistency Points + Fetal Station Points + Fetal Position Points
Cervical Dilation— Scored as: closed (0 points), 1–2 cm (1 point), 3–4 cm (2 points), ≥5 cm (3 points)Cervical Effacement— Scored as: 0–30% (0 points), 40–50% (1 point), 60–70% (2 points), ≥80% (3 points)Cervical Consistency— Scored as: firm (0 points), moderately firm (1 point), soft (2 points)Fetal Station— Scored as: −3 station (0 points), −2 station (1 point), −1 or 0 station (2 points), ≥+1 station (3 points)Fetal Position— Scored as: posterior (0 points), middle (1 point), anterior (2 points)
Interpreting Your Bishop Score
The Bishop score directly influences clinical decision-making regarding induction:
- Score ≥8 — Considered favourable. Vaginal delivery after induction is likely; success rates approximate those of spontaneous labour. Proceeding with induction using standard protocols is reasonable.
- Score 6–7 — Considered indeterminate. Clinical judgment is required. Some providers may attempt induction; others may recommend cervical ripening agents first.
- Score <6 — Considered unfavourable. Induction is less likely to succeed and carries increased risk of caesarean delivery. Cervical ripening or waiting for spontaneous labour onset is typically recommended.
Important: the Bishop score predicts likelihood, not certainty. Even with a favourable score, induction may not result in vaginal delivery. Conversely, unfavourable scores do not preclude successful vaginal delivery, particularly in patients who have previously delivered vaginally.
When and Why Labour Induction is Considered
Induction becomes necessary when the risks of continuing pregnancy outweigh the risks of delivery. Common indications include:
- Post-term pregnancy — beyond 42 weeks gestation, when placental insufficiency and stillbirth risk rise significantly
- Preeclampsia or gestational hypertension — conditions requiring prompt delivery for maternal safety
- Intrauterine growth restriction (IUGR) — when the baby is not growing adequately in the womb
- Maternal diabetes — to reduce risks of stillbirth and macrosomia
- Ruptured membranes — when amniotic fluid leaks and infection risk increases
- Multiple gestation — twins are typically delivered by 38–39 weeks; higher-order multiples even earlier
- Placental abruption or insufficiency — when the placenta is failing
The Bishop score helps clinicians determine whether induction is likely to succeed in these scenarios.
Important Considerations Before Induction
Understanding these practical factors ensures realistic expectations and safer labour management.
- Parity matters significantly — Women who have previously delivered vaginally have higher induction success rates even with lower Bishop scores. First-time mothers with unfavourable scores face substantially higher caesarean rates. Your obstetric history influences how aggressively induction is pursued.
- Cervical ripening takes time — If your Bishop score is unfavourable, cervical ripening medications (misoprostol or dinoprostone) require 12–24 hours to work. Patience and monitoring are essential. Rushing induction without adequate ripening increases unnecessary operative delivery.
- Bishop score alone doesn't determine outcomes — Maternal age, BMI, presence of contractions, and fetal well-being also influence success. A score of 7 in a 25-year-old multiparous woman differs substantially from the same score in a 42-year-old first-time mother.
- Induction isn't risk-free — Induction increases rates of hyperstimulation, uterine rupture, and operative delivery compared with spontaneous labour. These risks are generally acceptable when induction is medically indicated, but they remain important to understand before proceeding.