Bishop Score Calculator

What is the Bishop Score?

The Bishop Score, also called the Bishop's Score, cervix score, or pelvic score, is a pre-labor scoring system that was first introduced by Dr. Edward Bishop in 1964. It is used by obstetricians, midwives, and other healthcare providers to assess the readiness of the cervix for labor induction. The score helps predict whether an induction of labor will be successful, meaning whether it will result in a vaginal delivery rather than an unplanned cesarean section.

Dr. Edward Bishop published his original scoring system in the journal Obstetrics & Gynecology in August 1964 under the title "Pelvic Scoring for Elective Induction." His research demonstrated that women with higher pre-induction cervical scores had significantly better outcomes when labor was induced. The system was designed to be simple enough for routine clinical use while still being predictive enough to guide clinical decision-making.

The Bishop Score evaluates five key characteristics of the cervix and the position of the baby: cervical dilation, cervical effacement (thinning), fetal station (how far the baby has descended into the pelvis), cervical consistency (how firm or soft the cervix is), and cervical position (whether the cervix is pointed toward the back, middle, or front of the vagina). Each component is assigned a score, and these individual scores are summed to produce the total Bishop Score, which ranges from 0 to 13.

Over the past six decades, the Bishop Score has remained one of the most widely used clinical tools in obstetrics worldwide. Despite the development of more modern assessment methods, including transvaginal ultrasound measurement of cervical length and fetal fibronectin testing, the Bishop Score continues to be a cornerstone of clinical practice because of its simplicity, zero cost, and reasonable predictive accuracy. It requires no special equipment -- only a skilled examiner performing a digital cervical examination.

A Bishop Score of 8 or higher is generally considered "favorable," indicating that the cervix is ripe and that labor induction is likely to result in a successful vaginal delivery. A score of 6 or lower is considered "unfavorable," suggesting that the cervix is not yet ready for induction and that cervical ripening agents may be needed before proceeding. Scores of 6 to 7 fall into an intermediate zone where clinical judgment plays a larger role in determining the best course of action.

What Does "Induce Labor" Mean?

Labor induction is the process of artificially stimulating the uterus to begin contractions before labor starts naturally on its own. It is one of the most common obstetric interventions performed worldwide, with induction rates varying from approximately 20% to over 30% of all deliveries in many developed countries. The decision to induce labor is made when the benefits of delivering the baby sooner outweigh the risks of continuing the pregnancy.

There are several methods that can be used to induce labor, and the choice of method often depends on the Bishop Score and other clinical factors:

• Oxytocin (Pitocin) infusion: This is a synthetic form of the natural hormone oxytocin, which causes uterine contractions. It is administered intravenously and the dose is gradually increased until effective contractions are established. Oxytocin is most effective when the cervix is already favorable (high Bishop Score).
• Prostaglandin administration: Prostaglandins such as misoprostol (Cytotec) and dinoprostone (Cervidil, Prepidil) are used to soften and thin the cervix (a process called cervical ripening). They can be given orally, vaginally, or as a gel placed near the cervix. Prostaglandins are especially useful when the Bishop Score is low and the cervix needs to be prepared before active induction.
• Mechanical cervical dilation: A Foley catheter balloon can be inserted through the cervix and inflated to apply gentle pressure, which stimulates the cervix to dilate and releases natural prostaglandins. This method is particularly useful for women who cannot receive pharmacological prostaglandins (for example, women with a prior cesarean section scar).
• Amniotomy (breaking the water): This involves artificially rupturing the amniotic membranes using a small hook. It can stimulate labor by releasing prostaglandins and increasing pressure on the cervix. Amniotomy is usually performed when the cervix is already somewhat dilated and is often combined with oxytocin.
• Membrane sweeping (stripping): During a vaginal examination, the healthcare provider uses a finger to separate the amniotic membranes from the lower uterine segment. This releases prostaglandins and can encourage the onset of natural labor within 24 to 48 hours. While not a formal induction method, it is often used as a preliminary step.

The success of labor induction depends heavily on the state of the cervix at the time induction begins. This is precisely why the Bishop Score is so valuable: it provides an objective, standardized assessment of cervical readiness that helps clinicians choose the most appropriate induction method and counsel patients about what to expect. A woman with a favorable cervix (high Bishop Score) can generally expect a shorter induction time and a higher probability of vaginal delivery compared to a woman with an unfavorable cervix (low Bishop Score).

The Five Components of the Bishop Score

The Bishop Score is composed of five distinct components, each of which assesses a different aspect of cervical readiness and fetal positioning. Understanding each component is essential for interpreting the score and appreciating its clinical significance.

Cervical Dilation

Cervical dilation refers to how open the cervix is, measured in centimeters. During pregnancy, the cervix is normally closed (0 cm) to keep the baby safely inside the uterus. As labor approaches, the cervix begins to open (dilate) in response to hormonal changes and the pressure of the baby's head. Full dilation is 10 cm, at which point the baby can pass through the cervix into the birth canal.

For the Bishop Score, dilation is scored as follows:

• Closed (0 cm): 0 points -- The cervix has not begun to dilate at all. This is common in women who are far from the onset of labor.
• 1-2 cm: 1 point -- Early dilation has begun. This is a positive sign that the cervix is starting to change, though more progress is needed.
• 3-4 cm: 2 points -- Significant dilation. The cervix is well on its way, and active labor may begin soon or respond well to induction.
• 5+ cm: 3 points -- The cervix is substantially dilated. At this stage, the woman may already be in early labor, and induction is very likely to succeed.

Dilation is considered one of the most important components of the Bishop Score because it directly indicates how close the cervix is to being ready for delivery.

Cervical Effacement

Effacement is the process of the cervix becoming thinner and shorter. Before labor, the cervix is typically thick and about 3 to 4 centimeters long. As effacement progresses, the cervix gradually thins out and becomes incorporated into the lower uterine segment. Effacement is measured as a percentage, where 0% means no thinning has occurred and 100% means the cervix is paper-thin and fully effaced.

For the Bishop Score, effacement is scored as:

• 0-30%: 0 points -- The cervix is still thick and has undergone little or no thinning.
• 40-50%: 1 point -- Moderate thinning has begun.
• 60-70%: 2 points -- Substantial thinning; the cervix is approaching readiness.
• 80%+: 3 points -- The cervix is very thin, indicating excellent readiness for labor.

Effacement and dilation often progress together, though effacement typically begins before significant dilation in first-time mothers. In women who have given birth before, these processes may occur simultaneously.

Fetal Station

Fetal station describes the position of the baby's presenting part (usually the head) relative to the ischial spines of the mother's pelvis. The ischial spines are bony landmarks on either side of the pelvis that serve as the narrowest point of the birth canal. Station is measured on a scale from -5 to +5 (or sometimes -3 to +3 in a simplified system), where 0 represents the level of the ischial spines.

Negative numbers indicate the baby's head is above the ischial spines (still high in the pelvis), while positive numbers mean the baby has descended past the ischial spines (closer to delivery). For the Bishop Score, station is scored as:

• -3: 0 points -- The baby's head is floating high above the pelvis, far from engagement.
• -2: 1 point -- The baby is beginning to descend into the pelvis.
• -1 to 0: 2 points -- The baby is engaged in the pelvis, at or near the level of the ischial spines.
• +1 to +2: 3 points -- The baby has descended well past the ischial spines and is close to delivery.

A lower (more engaged) fetal station is favorable because it means the baby is applying pressure to the cervix, which helps stimulate further dilation and effacement.

Cervical Consistency

Cervical consistency refers to how firm or soft the cervix feels during a digital examination. During most of pregnancy, the cervix is firm (similar to the tip of your nose) due to its high collagen content. As labor approaches, hormonal changes (particularly the action of prostaglandins) cause the collagen fibers in the cervix to break down and rearrange, making the cervix progressively softer.

For the Bishop Score, consistency is scored as:

• Firm: 0 points -- The cervix feels rigid and resistant, similar to the tip of the nose. This is typical early in pregnancy or when the cervix is not yet ripening.
• Medium: 1 point -- The cervix has intermediate softness, similar to the feel of an earlobe. Some ripening has occurred.
• Soft: 2 points -- The cervix is very soft and pliable, similar to the feel of the inside of a cheek. This indicates advanced cervical ripening and readiness for labor.

A soft cervix is more likely to dilate readily in response to the pressure of contractions, making it a favorable finding for labor induction.

Cervical Position

Cervical position describes the orientation of the cervix within the vagina. Before labor begins, the cervix is typically positioned toward the back of the vagina (posterior). As labor approaches, the cervix gradually moves forward to a central (mid) position and eventually to an anterior position, pointing toward the front of the vagina. An anterior cervix is easier to access during examination and is aligned with the direction of the baby's descent.

For the Bishop Score, position is scored as:

• Posterior: 0 points -- The cervix is pointing toward the mother's back, making it more difficult to reach during examination and less favorable for induction.
• Mid-position: 1 point -- The cervix is in an intermediate position, having begun to move forward.
• Anterior: 2 points -- The cervix is pointing toward the front of the vagina, in the most favorable position for labor and delivery.

Bishop Score Scoring Table

The following table provides a complete summary of the Bishop Score components and their point values. This standardized table is used in clinical settings worldwide to ensure consistent assessment and documentation.

Note that cervical consistency and cervical position have a maximum of 2 points each, while dilation, effacement, and station can each score up to 3 points. This gives a maximum possible total of 3 + 3 + 3 + 2 + 2 = 13 points.

How to Interpret the Bishop Score

The interpretation of the Bishop Score is critical for clinical decision-making regarding labor induction. The total score guides healthcare providers in determining the best approach for each individual patient.

Score 0-5: Unfavorable Cervix

A Bishop Score of 0 to 5 indicates an unfavorable or "unripe" cervix. At this stage, the cervix has not undergone sufficient changes to respond well to labor induction with oxytocin alone. Research shows that inducing labor when the Bishop Score is 5 or below is associated with:

• Longer duration of labor induction (often 12-24+ hours)
• Higher rates of failed induction
• Increased risk of cesarean delivery (some studies suggest rates as high as 40-50% with very low scores)
• Greater likelihood of needing additional interventions

For women with unfavorable cervices, cervical ripening agents are typically recommended before beginning oxytocin induction. These agents help prepare the cervix by softening, thinning, and partially dilating it, effectively raising the Bishop Score before formal induction begins.

Score 6-7: Intermediate

A score in the intermediate range suggests that the cervix is partially prepared for labor. Induction may be considered, but the approach should be individualized based on the specific clinical situation, the urgency of delivery, and patient preferences. Some providers may choose to proceed with induction directly, while others may opt for a brief course of cervical ripening to improve the chances of success.

Score 8-13: Favorable Cervix

A Bishop Score of 8 or higher indicates a favorable or "ripe" cervix that is well-prepared for labor. At this score level:

• The probability of successful vaginal delivery after induction is very high (similar to spontaneous labor)
• Induction can typically proceed directly with oxytocin and/or amniotomy
• The duration of labor induction is generally shorter
• The cesarean delivery rate is significantly lower compared to women with unfavorable cervices

In Dr. Bishop's original study, he found that women with a score of 9 or higher had a nearly 100% success rate with elective induction, with most delivering within a few hours of starting oxytocin. Even with slightly lower scores in the favorable range, success rates remain very high.

Modified Bishop Score

Over the years, several modifications to the original Bishop Score have been proposed and used in clinical practice. The most commonly referenced modification simplifies the scoring system while attempting to maintain or improve its predictive value.

The Modified Bishop Score, sometimes called the Simplified Bishop Score, differs from the original in several ways:

• Station scoring: Some modified versions use a -5 to +5 scale instead of the -3 to +3 scale, with different point assignments.
• Effacement measurement: Some versions replace percentage-based effacement with cervical length in centimeters, as measured either digitally or by transvaginal ultrasound.
• Simplified categories: Some modifications reduce the number of categories for each component or combine related findings.
• Additional factors: Some extended versions include additional variables such as maternal parity (whether this is a first pregnancy or a subsequent one), gestational age, or the presence of preeclampsia.

Research comparing the original and modified Bishop Scores has shown mixed results. Some studies suggest that the modified versions offer improved predictive accuracy, particularly when combined with other assessment tools like transvaginal ultrasound cervical length measurement. However, the original Bishop Score remains the most widely used and recognized version in clinical practice.

One important consideration is that no single scoring system is perfect. The Bishop Score has moderate sensitivity and specificity for predicting induction success, and individual patient factors (such as parity, body mass index, gestational age, and the indication for induction) can significantly influence outcomes regardless of the cervical score. For this reason, the Bishop Score should always be interpreted in the broader clinical context rather than used as the sole determinant of management decisions.

Cervical Ripening Methods

When the Bishop Score indicates an unfavorable cervix (typically a score of 6 or below), cervical ripening is usually recommended before proceeding with oxytocin induction. Cervical ripening is the process of preparing the cervix to become softer, thinner, and more dilated, thereby improving the chances of a successful induction. There are two main categories of cervical ripening methods: pharmacological and mechanical.

Pharmacological Methods

Prostaglandin E2 (Dinoprostone): Dinoprostone is available in several forms, including a vaginal gel (Prepidil), a vaginal insert (Cervidil), and an intracervical gel. Cervidil is one of the most commonly used products; it is a thin, flat insert that releases a controlled dose of dinoprostone over 12 hours. It has the advantage of being removable if hyperstimulation (excessively strong or frequent contractions) occurs. Dinoprostone works by softening the cervical collagen matrix, increasing the water content of the cervix, and stimulating mild uterine contractions.

Prostaglandin E1 (Misoprostol): Misoprostol (brand name Cytotec) is a synthetic prostaglandin E1 analogue that was originally developed for the prevention and treatment of gastric ulcers. However, it has become widely used in obstetrics for cervical ripening and labor induction due to its effectiveness, low cost, stability at room temperature, and multiple routes of administration (oral, sublingual, vaginal, rectal). Typical doses for cervical ripening range from 25 to 50 micrograms given vaginally or 25 to 50 micrograms given orally every 3 to 6 hours.

Misoprostol is generally more effective than dinoprostone in achieving vaginal delivery within 24 hours, but it is associated with a higher risk of uterine hyperstimulation and tachysystole (excessively frequent contractions). For this reason, careful dosing and continuous fetal monitoring are essential. Misoprostol should be used with extreme caution, or not at all, in women with a prior cesarean section or other uterine surgery due to the risk of uterine rupture.

Mechanical Methods

Foley Catheter (Transcervical Balloon): A Foley catheter is a thin, flexible tube with an inflatable balloon at its tip. For cervical ripening, the catheter is inserted through the cervix and the balloon is inflated with 30 to 80 milliliters of saline on the internal side of the cervix. The balloon applies gentle, constant pressure to the internal cervical os, stimulating the release of local prostaglandins and mechanically dilating the cervix. The catheter typically falls out on its own once the cervix dilates to 3-4 cm, at which point oxytocin induction can begin.

The Foley catheter method has several advantages: it has a very low risk of uterine hyperstimulation, it does not increase the risk of uterine rupture in women with prior cesarean sections, it is inexpensive, and it has been shown to be equally effective as pharmacological methods in many studies. It can also be used in combination with misoprostol or oxytocin for enhanced effectiveness.

Double-Balloon Catheter (Cook Cervical Ripening Balloon): This is a specialized device with two balloons -- one that sits above the internal cervical os and one that sits below it in the vagina. Both balloons are inflated, providing bidirectional pressure on the cervix. Some studies suggest this may be slightly more effective than the single Foley balloon, though the evidence is not conclusive.

Hygroscopic Dilators (Laminaria): These are thin sticks made from dried seaweed (laminaria) or synthetic osmotic material that are inserted into the cervical canal. They absorb moisture from the cervical tissue and gradually swell over several hours, mechanically dilating the cervix. Laminaria are more commonly used for cervical preparation before surgical procedures (such as dilation and evacuation) than for labor induction.

When is Labor Induction Recommended?

Labor induction is recommended in a variety of clinical situations where the risks of continuing the pregnancy outweigh the risks associated with delivery. The decision is always made on an individual basis, taking into account the specific medical situation, gestational age, and maternal and fetal well-being. Common indications for labor induction include:

• Post-term pregnancy (past 41-42 weeks): After 41 weeks of gestation, the risks of stillbirth, meconium aspiration, and macrosomia (excessively large baby) increase significantly. Most guidelines recommend induction between 41 and 42 weeks to reduce these risks.
• Preeclampsia and gestational hypertension: These conditions involve high blood pressure during pregnancy and can lead to serious complications for both mother and baby, including seizures (eclampsia), stroke, liver and kidney failure, and placental abruption. Delivery is often the definitive treatment, and induction is recommended when the condition is severe or when gestational age is appropriate.
• Premature rupture of membranes (PROM): When the amniotic membranes rupture (water breaks) before labor begins, particularly at or near term, induction is often recommended to reduce the risk of infection (chorioamnionitis) for both mother and baby.
• Gestational diabetes: Poorly controlled gestational diabetes can lead to macrosomia and other complications. Induction is sometimes recommended at 39-40 weeks, particularly if the estimated fetal weight is large or blood sugar control has been suboptimal.
• Fetal growth restriction (IUGR): When the baby is not growing adequately in the uterus, delivery may be recommended to prevent further deterioration of fetal well-being. The timing depends on the severity of the growth restriction and gestational age.
• Oligohydramnios: Low amniotic fluid levels can indicate problems with placental function and may compromise the baby's well-being. Induction may be recommended depending on the severity and gestational age.
• Cholestasis of pregnancy: This liver condition causes intense itching and elevated bile acids during pregnancy. It is associated with an increased risk of stillbirth, particularly after 37 weeks, so early delivery by induction is often recommended.
• Elective induction at 39+ weeks: The ARRIVE trial (A Randomized Trial of Induction Versus Expectant Management) demonstrated that elective induction at 39 weeks in low-risk first-time mothers may actually reduce the risk of cesarean delivery and hypertensive disorders compared to expectant management. This finding has led to increased acceptance of elective induction at 39 weeks, though practice varies by institution and provider.
• Maternal medical conditions: Chronic hypertension, kidney disease, cardiac disease, autoimmune conditions, and other maternal medical problems may necessitate planned delivery before the due date.
• Fetal conditions: Certain fetal diagnoses (such as congenital anomalies requiring postnatal surgery) may require planned delivery at a specific gestational age and location where appropriate neonatal care is available.

Risks of Labor Induction

While labor induction is generally safe when performed for appropriate indications, it is not without risks. Understanding these risks is important for informed decision-making and for putting the Bishop Score in context as a tool that helps minimize complications by identifying women who are most likely to have a successful induction.

• Failed induction and cesarean delivery: The most common adverse outcome of labor induction is failure to achieve adequate labor progress, leading to cesarean delivery. The risk of cesarean is highest when the Bishop Score is low and the cervix is unfavorable. This is precisely why the Bishop Score is so valuable -- it helps identify women who need cervical ripening before induction and sets appropriate expectations.
• Uterine hyperstimulation (tachysystole): Induction medications, particularly oxytocin and prostaglandins, can cause the uterus to contract too frequently (more than 5 contractions in 10 minutes) or too strongly. This can reduce blood flow to the baby, causing fetal distress (abnormal fetal heart rate patterns). Management includes reducing or stopping the induction medication, repositioning the mother, giving IV fluids, and in some cases, administering a tocolytic medication (terbutaline) to relax the uterus.
• Uterine rupture: This is a rare but potentially catastrophic complication in which the uterine wall tears. The risk is highest in women who have had a prior cesarean section or other uterine surgery, particularly when prostaglandins are used for induction. For this reason, induction protocols in women with prior cesarean scars typically avoid prostaglandins or use them with extreme caution.
• Cord prolapse: If amniotomy is performed when the baby's head is not well engaged in the pelvis, there is a small risk that the umbilical cord can slip past the baby's head (cord prolapse), which is an obstetric emergency requiring immediate cesarean delivery.
• Maternal infection: Prolonged labor induction, particularly after rupture of membranes, increases the risk of chorioamnionitis (infection of the amniotic membranes and fluid), which can affect both mother and baby.
• Postpartum hemorrhage: Induced labors, especially those that are prolonged, may have a slightly higher risk of postpartum hemorrhage (excessive bleeding after delivery) compared to spontaneous labor.
• Neonatal admission: Babies born after induction, particularly at early gestational ages, may have a slightly higher risk of requiring admission to the neonatal intensive care unit (NICU) compared to those born after spontaneous labor at the same gestational age.

It is important to emphasize that for most indications, the risks of induction are substantially lower than the risks of continuing the pregnancy. The Bishop Score helps optimize the induction process by guiding the choice of ripening and induction methods, ultimately reducing the likelihood of complications.

Bishop Score in Practice: Clinical Examples

To illustrate how the Bishop Score is used in real clinical scenarios, consider the following examples:

Example 1: First-time Mother at 41 Weeks

A 28-year-old woman in her first pregnancy presents at 41 weeks and 3 days of gestation for a scheduled induction due to post-term pregnancy. On cervical examination, the findings are: dilation 1 cm, effacement 40%, station -2, consistency medium, position mid. The Bishop Score is calculated as: 1 + 1 + 1 + 1 + 1 = 5.

With a score of 5 (unfavorable), the obstetrician recommends cervical ripening before beginning oxytocin. A Foley catheter is placed transcervically and left in place overnight. The next morning, the Foley has fallen out, and re-examination reveals: dilation 3 cm, effacement 60%, station -1, consistency soft, position anterior. The new Bishop Score is: 2 + 2 + 2 + 2 + 2 = 10 (favorable). Oxytocin induction is started, and the patient delivers vaginally 8 hours later.

Example 2: Multiparous Woman with Preeclampsia

A 34-year-old woman in her third pregnancy is diagnosed with preeclampsia at 37 weeks. Delivery is recommended. On examination: dilation 2 cm, effacement 70%, station -1, consistency soft, position anterior. Bishop Score: 1 + 2 + 2 + 2 + 2 = 9 (favorable).

Given the favorable Bishop Score and the fact that she has had two prior vaginal deliveries, the team proceeds directly with amniotomy followed by low-dose oxytocin. She delivers vaginally within 4 hours.

Example 3: Elective Induction at 39 Weeks

A 30-year-old first-time mother requests elective induction at 39 weeks after discussing the ARRIVE trial findings with her provider. On examination: dilation 0 cm, effacement 20%, station -3, consistency firm, position posterior. Bishop Score: 0 + 0 + 0 + 0 + 0 = 0 (very unfavorable).

With such a low Bishop Score, the provider counsels the patient that induction at this time would likely be prolonged and has a higher risk of cesarean delivery. They discuss the option of waiting another week to see if the cervix ripens naturally, or beginning with an outpatient cervical ripening approach using a Foley catheter or scheduled misoprostol. The patient elects to wait one week and return for reassessment.

Frequently Asked Questions