The Bishop Score is a widely used system in obstetrics developed by Dr. Edward Bishop in 1964. It assesses the readiness of a pregnant person’s cervix for labor. This scoring mechanism provides a standardized way for clinicians to evaluate the physical state of the cervix and the baby’s position in the pelvis. Its main purpose is to predict the likelihood of a successful vaginal delivery when labor induction is being considered.
The Five Key Components of the Score
The Bishop Score calculation involves a physical examination evaluating five specific characteristics. These factors are cervical dilation, cervical effacement, cervical consistency, cervical position, and the baby’s fetal station. Points are assigned to each component, typically ranging from zero to three, based on the physical findings observed by the clinician.
Cervical dilation measures how open the cervix is, quantified in centimeters. A higher score is given for greater opening, as the cervix must dilate to 10 centimeters for delivery. Cervical effacement refers to the thinning and shortening of the cervix, measured as a percentage. For example, 100% effacement means the cervix is paper-thin. A higher percentage of effacement earns more points because it indicates the cervix has begun the natural preparation process.
Cervical consistency assesses the texture of the cervix, determining if it is firm, medium, or soft. A softer, more pliable cervix receives a higher score because it is more likely to stretch and open during labor. The position of the cervix is also evaluated as posterior (tilted toward the back), mid-position, or anterior (tilted toward the front). The cervix naturally moves from a posterior to an anterior position as the body prepares for labor, making the forward-facing position more favorable.
Fetal station measures the baby’s descent into the pelvis relative to the ischial spines, which are bony points within the mother’s pelvis. This measurement is expressed in negative or positive numbers. Zero station indicates the baby’s head is level with the spines.
A negative number means the baby is high in the pelvis, while a positive number means the baby has descended further. A lower station is associated with a higher score. The total Bishop Score is determined by adding the points from these five factors, ranging from zero to 13.
Interpreting Bishop Score Results
The total Bishop Score predicts how favorable conditions are for a successful labor induction. A higher score suggests the cervix is biologically “ripe” and likely to respond well to induction methods. Scores are typically divided into three main ranges, each implying a different likelihood of a successful vaginal delivery following induction.
A low score, generally five or less, indicates the cervix is unfavorable or unripe for induction. In this range, the likelihood of a successful vaginal delivery is lower, and the induction process may take significantly longer. This low score often suggests that cervical ripening will be necessary before the actual induction can begin.
Scores in the moderate range, usually six or seven, suggest a transitional state where the cervix is beginning to prepare for labor. The success rate for induction improves compared to a low score, but the outcome may still be uncertain. The decision to proceed directly to induction or perform cervical ripening first often depends on other maternal and fetal health factors.
A high score, typically eight or more, is considered favorable and indicates a high probability of a successful induction. A score in this range means the cervix is already soft, significantly effaced, and possibly dilated, mirroring the physical changes that occur just before spontaneous labor. For individuals with a high Bishop Score, the success rate of induction is comparable to spontaneous labor, and the process is generally shorter.
Clinical Role in Labor Management
The Bishop Score is a fundamental guide for clinicians planning a labor induction, directly influencing the choice of management strategy. When a patient presents with a low score of five or less, the medical team recognizes the need for pre-induction steps to physically soften and prepare the cervix. These preparatory interventions, known as cervical ripening, are designed to chemically or mechanically alter the cervix to increase the score before administering labor-inducing medication.
Common cervical ripening methods include pharmacological agents, such as prostaglandins, inserted vaginally or taken orally to soften the cervix. Mechanical methods, like balloon catheters, may also be used to physically dilate the cervical opening and exert pressure. Using the Bishop Score to mandate this ripening phase for low-scoring patients significantly improves the chances of a successful vaginal delivery and reduces the risk of a prolonged, unsuccessful induction that could result in a cesarean delivery.
Conversely, a high score of eight or more allows the clinician to bypass cervical ripening and proceed directly to methods designed to stimulate uterine contractions. This typically involves administering synthetic oxytocin intravenously, which is a more direct induction method. The score serves as a tool for patient counseling, providing an evidence-based assessment of the expected duration and likelihood of success for the induction process. This prediction helps manage expectations and informs the patient’s understanding of their labor journey.