Bishops Score and Induction of Labor

Back in 1964, Edward Bishop came up with a checklist for inducing labor, which included things like how many babies the mom has had before, how far along the pregnancy is, the baby's position, mom's medical history, (and of course her consent). He also created a scoring system, known as the Bishop score, to predict if labor induction would be successful.

Here's how it works: Before a labor induction, a cervical exam is done to check if the cervix needs to be ripened before starting the induction process. A ripe cervix is soft and stretchy and indicates that changes are happening in advance of your labor starting.

1. Bishop Score Criteria:

   1. Cervical Dilation: How open the cervix is (measured in centimeters).

   2. Effacement: How thin the cervix has become (expressed in percentage).

   3. Fetal Station: The baby's position relative to the mother's pelvis (-2)

   4. Cervical Position: The cervix's position in relation to the baby's head and mother's pelvis (anterior, mid or posterior).

   5. Cervical Consistency: How the cervix feels (firm or soft).

Why is the Bishop Score Important?

Traditionally a Bishop score (8 or more) was thought to mean that your cervix is likely ready for labor, and inducing labor has a good chance of leading to a vaginal birth. A low score suggests that your cervix isn’t quite ready, and your OB might recommending methods to ripen (soften) your cervix before induction. Keep in mind the ripening process can take several days before you start to dilate and can be painful.

• 8 or more points. Bishop scores above eight indicate labor will most likely start spontaneously (and soon). It also indicates that if an induction is necessary, it will more than likely be successful.

• 6 to 7 points. Bishop scores in this range aren’t a great predictor one way or the other.

• 5 or fewer points. Low Bishop scores indicate that an induction is less likely to be successful.

Is the Bishops Score Still Relevant Today?

The paper "Reassessing the Bishop score in clinical practice for induction of labor leading to vaginal delivery and for evaluation of cervix ripening" evaluates the relevance of the Bishop score, in modern obstetric practice. They have some valid points to consider.

1. Historical Context and Original Purpose:

   • Originally, the score was designed for multiparous women at term (they have given birth before) who had previous vaginal births and included five criteria: cervix dilation, effacement, consistency, position, and station.

   • In those days (1960s) induction methods really only included synthetic oxytocin, membrane stripping/sweep, and amniotomy (breaking the waters). Bishop found that a score of 9 or more predicted successful induction with labor lasting less than 4 hours.

2. Expanded Use and Modern Obstetric Practices:

   • The Bishop score has been widely adopted and modified for use in first time moms (including preterm labor).

   • Modern induction methods and advances in labor management have improved maternal and newborn outcomes (in some countries), raising questions about the predictive value of the original Bishop score in modern practice.

3. Demographic Differences:

   • The original Bishop score was based on a demographic of moms that differs significantly from today’s diverse and sometimes medically complex population.

   • Modern IOL is often done for specific maternal or fetal indications (e.g., hypertension, fetal growth restriction), not just elective reasons.

   • Current outcomes for IOL usually take longer than the 4 hours observed in Bishop’s time, and methods of induction have evolved.

4. New IOL Approaches:

   • New pharmacologic agents and mechanical methods for cervical ripening (e.g., prostaglandins, rods, balloon catheters) differ significantly from the methods used in Bishop’s original studies.

   • The correlation between a low Bishop score and higher cesarean delivery rates is not always consistent with modern findings (in my experience a low Bishops score (below 4) is likely to be a longer more difficult labor for mom (and baby).

   • (Note - I’ve supported mums through very positive medically indicated inductions with scores of 3 and less. But I think part of what made this successful was making peace with the decision and accepting the medical help so there was no emotional resistance). This is a really good reason to practice mindful acceptance and self-compassion. The mind influences our mindset and our labor.

5. Post-Ripened Cervical Dilatability:

   • The cervix is a unique structure, and its remodeling/softening before labor involves complex biochemical changes.

   • Research indicates that cervical softening begins long before the onset of labor.

   • Studies suggest that the Bishop score may not fully capture the readiness of the cervix for labor, as it primarily reflects post-ripening dilation rather than the entire remodeling process.

6. Alternative Approaches to Pre-Induction Cervical Evaluation:

   • The paper suggests exploring new methods to assess cervical readiness for labor, including:

     • Cervical Length (CL): Measured via transvaginal ultrasound, which can predict preterm birth and labor outcomes.

     • Elastography: Evaluates the stiffness of cervical tissue (a ripe cervix will feel soft like your lips - unripe feels more like your nose).

     • Raman Spectroscopy: Assesses molecular changes in the cervix during pregnancy.

     • Biomolecular Markers: Identifies inflammatory processes and structural changes in the cervix.

In a nutshell researchers are calling for a reassessment of the Bishop score’s utility in modern obstetric practice, advocating for the integration of new technologies and markers to better predict cervical readiness for labor. This would help tailor induction procedures to optimize outcomes for moms and babies.

And of course, don’t forget - if all is well you can choose to wait a bit longer. Your body has done such a great job of keeping your baby in for 9 months - forcing your body to try and open can also sometimes lead to unhappy babies who can’t tolerate the intensity of an induction. But, if there’s a compelling medical reason to induce, do your best to shift your mindset to acceptance and write down 5 benefits of having the induction. As we say in GentleBirth - control the controllables.

Tracy