Bishop’s Score and Cervical Ripening for Induction of Labor

If you and your care provider have decided that an induction of labor is the right choice for you (either electively or for medically indicated reasons), you have options! There are many ways to induce labor, depending on your starting point. This starting point is called your Bishop’s score.

Bishop's Score is a pre-labor scoring system used to assess the readiness of the cervix for labor. It evaluates five components: consistency, position, cervical dilation, effacement, and fetal station. A score of 8 or higher indicates a favorable cervix, while a score below 6 suggests an unfavorable cervix that may benefit from cervical ripening before induction [Tenore, 2003].

This calculator show’s you how these factors are assigned points and your score is calculated.

As your body prepares for birth, your cervix will move from facing posterior (pointing towards your back) to anterior (pointing towards the front of your body). A posterior cervix is assigned 0 points, a midline cervix 1 point, and an anterior cervix 2 points.

The consistency of your cervix refers to how it feels upon exam. Your cervix will begin to change from being firm (feeling like the tip of your nose) to being soft. A firm cervix gets assigned 0 points, a cervix beginning to soften (medium) 1 point, and a completely softened cervix receives 2 points.

Effacement is how thin and short your cervix is. Before pregnancy and during pregnancy, it is 0%. During labor, it will shorten and thin - a process I like to describe as “melting away.” When your cervix is 100% effaced, it is very thin and soft. For a first time birther, their cervix will typically efface before the cervix begins to dilate. For people who have given birth before, dilation and effacement usually happen at the same time.

*The Bishop’s Score only accounts for dilation between 0 - 6 centimeters. The reason for this is because some people can be 6 centimeters and not be in labor (typically people who have given birth multiple times).

Dilation scoring:

0 cm - 0 points

1-2 cm - 1 point

3-4 cm - 2 points

5-6 cm - 3 points

Effacement scoring:

0-30% - 0 points

40-50% - 1 point

60-70% - 2 points

80-100% - 3 points

The last aspect of a Bishop’s score is fetal station. This number is calculated by the baby’s position in your pelvis relative to a bony landmark called the ischial spines. A score of -3 or below (meaning the baby is high in your pelvis) is assigned 0 points.

-2 station - 1 point

-1 or 0 - 2 points

+1 or +2 - 3 points

When your baby is +3, they are beginning to crown.

If your cervix is “unfavorable,” meaning your body has not released the amount of prostaglandin hormone necessary for softening and opening your cervix for birth, you will be offered a cervical ripening agent.

There are two methods used for cervical ripening.

Foley Balloon Induction

Foley balloon catheters work by applying mechanical pressure to the cervix to stimulate dilation. Key findings include:

• Success rate: 70-80% achieve vaginal delivery within 24 hours

• Length of labor: Mean time from insertion to delivery is 21-23 hours

• Advantages: Lower risk of uterine hyperstimulation compared to prostaglandins. Safe for TOLAC/VBAC.

Prostaglandin Induction

Prostaglandins like dinoprostone (PGE2) work biochemically to soften and dilate the cervix. Key findings include:

• Success rate: 60-70% achieve vaginal delivery within 24 hours

• Length of labor: Mean time from insertion to delivery is 15-18 hours

• Advantages: May lead to faster labor onset compared to Foley balloon

Combined Method

Using both mechanical and pharmacological methods together has shown promising results:

• Success rate: Up to 83% achieve vaginal delivery within 24 hours

• Length of labor: Mean time from induction to delivery of 12-14 hours

• Advantages: May reduce time to delivery compared to either method alone.

While all methods can be effective, the combined approach appears to offer the highest success rates and shortest induction-to-delivery times.

However, you may choose a foley balloon induction because you would prefer to avoid synthetic hormones. Uterine hyperstimulation (also known as uterine tachysystole) can be very painful. People who experience this often describe it as feeling like there is no break between contractions and they are “one on top of another.”

Some people may choose to avoid a foley balloon because they do not want to have something inside of them for a long period of time. A foley balloon may not be possible if your baby’s head has already descended quite low into your pelvis.

This should not be interpreted as medical advice. Foley catheter balloons and prostaglandin medications are both safe and effective methods for induction of labor. This is only meant to serve as a guide so that you are aware of your options and can make a choice based on information and intuition.

Sources:

Chen, W., Xue, J., Peprah, M. K., Wen, S. W., Walker, M., Gao, Y., & Tang, Y. (2016). A systematic review and network meta-analysis comparing the use of Foley catheters, misoprostol, and dinoprostone for cervical ripening in the induction of labour. BJOG: An International Journal of Obstetrics & Gynaecology, 123(3), 346-354.

Diguisto, C., Le Gouge, A., Arthuis, C., Winer, N., Parant, O., Poncelet, C., ... & Perrotin, F. (2021). Cervical ripening in prolonged pregnancies by silicone double balloon catheter versus vaginal dinoprostone slow release system: The MAGPOP randomised controlled trial. PLoS Medicine, 18(2), e1003448.

Eser, A., Ozkaya, E., Abide, C. Y., Eser, T., Eser, G. Y., Abike, F., ... & Eroglu, M. (2019). Transcervical Foley balloon catheter and vaginal prostaglandin E2 insert combination vs. vaginal prostaglandin E2 insert only for induction of labor at term: a randomized clinical trial. Archives of Gynecology and Obstetrics, 299(2), 451-457.

Noor, N., Ansari, M., Ali, S. M., & Parveen, S. (2015). Foley catheter versus vaginal misoprostol for labour induction. International Journal of Reproductive Medicine, 2015, 845735.

Shetty, S. J., Spandana, J. C., Arpana, A., & Sathyanarayana, C. (2022). Comparative study of Foley's catheter and prostaglandin E2 gel for pre-induction cervical ripening. Asian Journal of Medical Sciences, 13(4), 35-41.

Wang, L., Wang, G., Cao, W., Guo, L., Hu, H., Li, Y., & Zhang, Q. (2020). Comparison of the Cook vaginal cervical ripening balloon with prostaglandin E2 insert for induction of labor in late pregnancy. Archives of Gynecology and Obstetrics, 302(2), 349-356.