Bishop Score Calculator

How does this Bishop score calculator work?

This is a health tool that evaluates the possibility of a successful vaginal delivery and whether labor needs to be induced. It is also used to assess spontaneous pre term delivery odds in certain pregnant women.

The Bishop score was published in the early 60s by Dr. Edward Bishop and has been known also under the terms pelvic or cervix score.

The Bishop score calculator comprises of both the original and the modified version which can be found in the two tabs and which assess the following components evaluated during vaginal examinations:

■ Cervical dilation – The cervix is described as fully open and the mother can push at a dilation to 10 cm. Minor dilation should be starting days or even weeks before actual labor begins. Before labor, the dilation is very slow while after labor starts or is induced, dilation rate is faster.

■ Cervical effacement – Describes the degree of softening and thinning of the cervix, measured through cervical exam. Normally the cervix is 0% effaced while at 50% effacement the cervix is half of its original thickness. Vaginal delivery occurs at 100% cervical effacement.

■ Cervical consistency – Evaluated on a firmness scale, with the indication that the softer the cervix the likelihood of vaginal delivery.

■ Cervical position – Refers to the favorability to vaginal delivery given by the anterior cervix compared to the posterior position.

■ Fetal station – Describes the descent of the baby into the pelvis with the usage of an imaginary line drawn between the two extremities of the pelvic bones that is known as the zero line. When the fetus is above the imaginary line, it is in a minus station, if the baby is below the line, it is in a plus station.

The modified version adds 5 more characteristics:

■ Preeclampsia;

■ Each prior vaginal delivery – for multiparous women, the score becomes higher with each pregnancy;

■ Postdates pregnancy;

■ Nulliparity – for women who are at the first pregnancy the score is slightly modified;

■ Premature or prolonged rupture of membranes.

There is also a mnemonic for the above factors to consider known under “Call PEDS For Parturition = Cervical Position, Effacement, Dilation, Softness; Fetal Station.”

Bishop score interpretation

The prediction of the likelihood of labor occurring naturally and progressing into a successful vaginal delivery in pregnant women without any inducement medication is quantified in a numeric result.

The Bishop model is essentially a pre-labor scoring system that allows clinicians to determine whether the induction of labor is required.

Each component in the score is awarded a number of points as explained below:

At the same time, the added characteristics in the Modified Bishop Score, either add a number of points to the sum of those already factored in or subtract points, depending on which characteristic is applicable:

■ Preeclampsia (+1 point);

■ Each prior vaginal delivery (+1 point/delivery);

■ Postdates pregnancy (-1 point);

■ Nulliparity (-1 point);

■ Premature or prolonged rupture of membranes (-1 point).

In the original version, the highest achievable score is 13 while the lowest but very unlikely is 0.

There is an inverse correlation between the length of labor and the Bishop Score, therefore scores above the 9 point threshold tend to indicate a successful vaginal birth, while scores below 5 suggest that the patient requires some intervention, usually through a cervical ripening method to induce labor.

Essentially the guidelines for both the original study and the modified version are as follows:

■ Scores of less than 5 indicate labor is unlikely to start without induction.

■ Scores between 5 and 8 carry both indications of induced or spontaneous labor depending on other patient factors such as if membrane rupture is present or the regularity of contractions.

■ Scores above 9 are usually indicative of spontaneous labor.

It has also been researched that in normal condition, a woman with a score of 1 would not be expected to enter labor in the following three weeks of pregnancy.

Amongst other clinical indications are those for cervical ripening with prostaglandins when the Bishop score is below 5, the membranes are still intact and there are no regular contractions or those for labor induction with Pitocin when the Bishop score is equal to or above 5 and the membrane rupture has produced.

The following table presents the correlation between cesarean rates and Bishop scores in deliveries by first time mothers and women who have had past vaginal deliveries.

References

1) Bishop EH. (1964) Pelvic Scoring for Elective Induction. Obstet Gynecol; 24:266-8.

2) Laughon SK. et al. (2011) Using a Simplified Bishop Score to Predict Vaginal Delivery. Obstet Gynecol; 117(4): 805–811.

3) Crane JM. (2006) Factors predicting labor induction success: a critical analysis. Clin Obstet Gynecol; 49(3):573-84.

4) Hughey MJ, McElin TW, Bird CC. (1976) An evaluation of preinduction scoring systems. Obstet Gynecol; 48(6):635-41.