Using the Bishop's Score for Labor Success
Finding Ways to Evaluate a Mother's Readiness for Birth
Apr 22, 2009
While the rate of labor inductions and cesareans continues to climb, many childbirth experts are interested in using ways to determine if a mother's body is more or less likely to successfully labor if an induction is started.
One of these tools is known as the Bishop's Score. This tool measures certain components with regard to the mother's cervix and baby's position to evaluate her readiness for an induction and ultimately increase the chance of having a vaginal birth. This scoring system can also be used to determine the likelihood of spontaneous labor.
Components of the Bishop's Score:
- Cervical dilation (opening)
- Cervical effacement (thinning of the cervix)
- Cervical consistency (softness versus firmness)
- Cervical position - posterior versus anterior
- Fetal station - baby's head in relation to the mother's pelvis
Bishop's Scoring System:
Each of the components are evaluated with a vaginal exam on a scale of 0 thru 2 or 0 thru 3. The total possible points is 13. The above components are scored using the following system:
Dilation: 0cm = 0 points, 1-2cm = 1 point, 3-4cm = 2 points, >5cm = 3 points
Effacement: 0-30% = 0 points, 40-50% = 1 point, 60-70% = 2 points, 80% = 3 points.
Consistency: Firm = 0 points, Intermediate = 1 point, Soft = 2 points
Position: Posterior = 0 points, Intermediate = 1 point,. Anterior = 2 points.
Station -3 = 0 points,-2 or -1 = 1 point, 0 or +1 = 2 points,+2 = 3 points
Cervical dilation is measured by the care provider up to 10 cm. Each finger-width of cervical opening is considered to be 2cm of dilation.
Effacement is expressed in a percentage and describes the "thinness" or length of the cervix. A longer cervix length will be less effaced than a cervix that is very thin.
The consistency of the mother's cervix refers to the texture. Is it very soft and pliable? Or is it firm?
Cervical position refers to whether the cervix faces the mother's front or her back. If it is anterior, the cervix can more easily align itself to the birth canal for delivery. A posterior cervix will need to rotate to the anterior position prior to birth.
The fetal station refers to the position of the baby's head in relation to the mother's pelvis. It is expressed in centimeters. The highest pelvic station is -4, where the baby's head is floating above the mother's pelvis. Mid-pelvis is at 0 station, and below that is +1 thru +4 station. This score stops at +2 station which is about the lowest a baby will ever be prior to labor.
Modifications of Bishop's Score
Several modifications of this scoring system include the following:
- Each prior vaginal birth adds 1 point to the score.
- Pre-eclampsia (or pregnancy-induced hypertension) adds 1 point to the overall score.
- Postdates pregnancy subtracts 1 point
- First baby subtracts 1 point
- Preterm labor or prolonged rupture of membranes (water broken) subtracts 1 point
Interpreting Bishop's Score
If the mother gets a Bishop's score of 5 or less based on these components, it is not considered to be a positive indication for an induction. If the mother's Bishop score is 5 or less but there are medical indications for an induction, her care provider may recommend using a cervical ripening agent such as prostaglandin gel to help ripen her cervix. A Bishop's score of 8 or 9 is considered to be a favorable indicator that an induction would be successful.
Using this tool, along with other guidelines to limit elective inductions to the end of week 40 of pregnancy, has been shown to have a positive influence on reducing both inductions and cesareans. Be sure to ask about the use of Bishop's score to determine the possible success of your own induction before you have one.
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