Why assess the cervix before induction?
When labor needs to be induced, for example after 41 weeks or because of high blood pressure, the condition of the cervix strongly predicts whether induction will lead to a vaginal birth. Dr. Edward Bishop described a simple score in 1964 that is still the standard way to assess it.
The five components
| Component | 0 | 1 | 2 | 3 |
|---|---|---|---|---|
| Dilation | Closed | 1–2 cm | 3–4 cm | ≥5 cm |
| Effacement | 0–30% | 40–50% | 60–70% | ≥80% |
| Station | −3 | −2 | −1, 0 | +1, +2 |
| Consistency | Firm | Medium | Soft | |
| Position | Posterior | Mid | Anterior |
The total ranges from 0 to 13.
Worked example
A cervix that is 1 cm dilated, 40% effaced, at station −2, of medium consistency and in mid-position scores 1 + 1 + 1 + 1 + 1 = 5: unfavorable. The simplified score (dilation, station, effacement) is 3, also unfavorable.
Reading the score
| Score | Meaning | Usual plan |
|---|---|---|
| 8 or more | Favorable | Oxytocin and/or breaking the waters (amniotomy) |
| 6–7 | Borderline | Depends on the situation and parity |
| 6 or less | Unfavorable | Cervical ripening first |
With a favorable cervix, the chance of vaginal delivery after induction is close to that of spontaneous labor.
Cervical ripening methods
- Prostaglandins: misoprostol tablets or dinoprostone gel or insert soften and thin the cervix.
- Mechanical methods: a balloon catheter placed in the cervix gently dilates it, with a lower risk of overly strong contractions.
- Membrane sweeping at a prenatal visit near term can make spontaneous labor more likely.
The ARRIVE trial
In 2018, the ARRIVE trial found that elective induction at 39 weeks in first-time mothers at low risk did not increase cesarean rates and slightly reduced them. Since then, induction at 39 weeks is offered more often in the US, which makes cervical assessment more common.
Modified scores
Some versions add points for each previous vaginal birth and subtract points for preeclampsia, post-term pregnancy or a first pregnancy. The simplified Bishop score, using only dilation, station and effacement with a cutoff of 5, performs about as well as the full score.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.