What Is the Bishop Score and How Does It Factor into Labor?
No matter how much you prepare, it's impossible to know how your labor and delivery will look. One thing you can do, however, is learn as much as possible about what to expect during each stage of labor before your due date.
That's where the Bishop score can come in handy.
What is the Bishop score?
Midwives, doctors and other medical professionals often mention the Bishop score, or Bishop scale, while discussing how close a person is to labor. But if you're new to the process, you might be left feeling a little confused about what it actually is.
"Bishop's score, also called the cervix score, is a pre-labor scoring system to allow for establishing whether induction of labor will be required for a mom-to-be," said Gareth Nye B.Sc., Ph.D., a senior lecturer at the Chester Medical School and endocrinology theme lead for the Physiological Society in Chester, England.
The Bishop score was created in 1964 by OB-GYN Edward Bishop, M.D., to help better predict successful induction using five criteria. Some birthing centers use a modified Bishop score that was developed in 1982.
The system featured a comprehensive list of criteria that, when assessed together, helped determine the best time to induce labor. Part of the criteria was a cervical examination that came to be known as the Bishop score.
Today, the Bishop scoring system is used to determine the best time for labor induction (i.e., labor that is started artificially). The doctor will assess whether the pregnant woman's body and cervix are ready for labor. It is typically used after 40 weeks, according to Cleveland Clinic.
A higher Bishop score means a successful vaginal delivery is more likely using induction.
During the beginning stages of labor, the cervix begins to dilate in a process known as effacement. Normally, the cervix is long and relatively firm. In preparation for birth, the cervix widens and softens as the uterus begins to contract.
When a woman is ready to give birth, the cervix has opened and seems to disappear and become part of the uterus. It's known as 100 percent effaced or fully effaced. At this point, the cervix is paper thin.
The scoring system involves a digital exam of the cervix and includes the following five criteria:
- Cervical dilation
- Fetal station
A doctor will examine all of these factors and add them up to arrive at a score between 0 and 13.
"A Bishop's score over 9 suggests that labor will occur itself without assistance," Nye said. "Any number below 5 suggests labor will not progress unless induced."
How is the Bishop score measured?
A cervical exam, usually a physical exam, helps a physician assess the Bishop score. The physician inserts their fingers into the vagina—also called a digital cervical exam—to see how the cervix is positioned and how it feels. An ultrasound checks the position of the baby's head.
These two exams will help the doctor determine how much your cervix has dilated and if the baby's head has moved down into the birth canal. A negative number on the Bishop score means the baby's head is still too high.
Once your exam is complete, the physician can then calculate your score by assessing the dilation, position and effacement (how much your cervix has receded) of the cervix, along with the fetal position.
Based on how much your cervix has dilated, the physician will assign a score based on the following:
- Closed: 0 points
- 1-2 cm: 1 point
- 3-4 cm: 2 points
- 5 cm or more: 3 points
The physical exam will reveal where the cervix is positioned, and the physician will assign a score as follows:
- Posterior: 0 points
- Mid-position: 1 point
- Anterior: 2 points
A softened cervix is essential to a successful delivery, so the physician wants to feel its consistency. Based on that, they will score it as follows:
- Firm: 0 points
- Moderately firm: 1 point
- Soft: 2 points
The last of the cervix scores measures how far it has receded, using percentages:
- 0-30 percent: 0 points
- 40-50 percent: 1 point
- 60-70 percent: 2 points
- 80 percent or more: 3 points
This scoring system determines how far your baby's head has descended through the birth canal, using position numbers from -3 to 2:
- -3: 0 points
- -2: 1 point
- -1, 0: 2 points
- 1, 2: 3 points
These scores are added to determine your overall Bishop score, which will be a number between 0 and 13.
How do you interpret the Bishop score?
Essentially, the higher your score, the closer you are to being ready for induction. Scores of 8 and above are typically considered ready for induction.
Ultimately, your doctor, midwife or doula will be responsible for finding out and interpreting your Bishop score if you are either planning a labor induction or if you end up needing an induced labor. Either way, it's suggested that you have a preference, not a plan, so you can better handle any changes that occur during the birthing process.