The Bishop Score is a standardized system used in obstetrics to evaluate the physical readiness of the cervix for labor, especially when induction is being considered. This tool, also known as the Cervical Score, was developed by Dr. Edward Bishop in 1964 to provide an objective method for assessing a patient’s labor potential. A healthcare provider determines the final numerical result through a manual vaginal examination, assessing several factors related to the cervix and the baby’s position. This score helps clinicians make informed decisions about the safest and most effective approach to initiating labor.
The Core Purpose of the Bishop Score
The primary function of the Bishop Score is to predict the likelihood of a successful vaginal delivery following a labor induction procedure. Induction involves medically stimulating the uterus to begin contractions, and its success is dependent on the condition of the cervix. A cervix that is not “favorable” or “ripe” is less likely to respond well to induction methods that primarily stimulate contractions, such as intravenous oxytocin (Pitocin).
The score guides clinicians in determining the most appropriate induction strategy. If a patient has a low or “unfavorable” score, it suggests the cervix needs to be physically softened and thinned, a process known as cervical ripening. The medical team will use pharmaceutical agents or mechanical devices for ripening before attempting to stimulate contractions. Conversely, a high score suggests the cervix is prepared for labor, and induction can proceed directly with methods like oxytocin administration or amniotomy (breaking the water). Using the score helps reduce the risk of a failed induction, which could lead to prolonged labor or an unplanned cesarean delivery.
Calculating the Score: The Five Key Factors
The Bishop Score is calculated by assigning a numerical value to five distinct anatomical factors, with the total score ranging from 0 to 13. Each factor is graded on a scale of 0 to 3 points, with higher points indicating a more favorable condition for labor. The assessment is a detailed physical examination that looks for changes in the cervix that naturally occur before the onset of labor.
The first factor is Cervical Dilation, which measures the opening of the cervix in centimeters. A closed cervix receives zero points, while a dilation of 5 to 6 centimeters earns the maximum three points. The second factor is Cervical Effacement, which assesses the thinning and shortening of the cervix, typically measured in a percentage. A cervix that is 80% or more effaced receives the highest points, compared to a cervix that is only 0-30% effaced, which receives zero points.
The third factor is Cervical Consistency, which evaluates the firmness of the tissue. A soft cervix, which is more pliable and ready to stretch, is considered favorable and is assigned more points than a firm cervix. Cervical Position is the fourth factor, assessing whether the cervix is pointing backward (posterior) or forward (anterior). As labor approaches, the cervix moves toward an anterior position, which is more accessible and favorable for delivery.
The final factor is Fetal Station, which describes the baby’s head position relative to the mother’s pelvis. This measurement is expressed in centimeters, where “station 0” means the baby’s head is aligned with the ischial spines. A negative number means the head is high above the pelvis, receiving fewer points. A positive number means the head has descended further into the pelvis, receiving the maximum three points. These five individual scores are then summed to produce the final Bishop Score.
Interpreting the Results
The cumulative Bishop Score provides a clear indication of a patient’s cervical maturity and the likely outcome of an induction. The total score, which ranges from 0 to 13, is generally grouped into three clinical categories: unfavorable, moderate, and favorable.
A low or unfavorable score, typically 5 or less, suggests that the cervix is firm and closed, meaning the body is not yet prepared for labor. When the score is in this low range, induction using only oxytocin is unlikely to be successful, and the risk of a lengthy labor or a cesarean delivery is higher. For these patients, the medical team recommends a period of cervical ripening to physically alter the cervix before attempting to stimulate contractions.
Scores in the moderate range, often between 6 and 7, indicate intermediate readiness for induction. Clinicians may still opt for mild cervical ripening before proceeding to stronger induction methods. A score of 8 or higher is considered favorable or ripe, signifying a cervix that is already soft, thin, and partially open. Patients in this high range have a greater chance of a successful vaginal delivery, and labor can usually be initiated directly with agents like Pitocin.