Which factors are included in patient evaluation when considering induction of labor using the Bishop score quizlet?

There are several different methods that medical professionals can use to induce labor.

Sweep your membranes

Before offering medical induction, your doctor or midwife may offer to sweep your membranes. During this procedure, your healthcare provider inserts their finger into your vagina and through your cervix if they find that it’s already slightly open. They manually separate the amniotic sac from the lower part of your uterus, which is thought to cause the release of prostaglandins. The release of prostaglandins may ripen your cervix and possibly get your contractions going.

Some women find sweeps extremely uncomfortable. There’s an increased risk of infection and there is no evidence that they are effective. There’s also a risk that the water can break. Delivery should occur within about 24 hours of the water breaking to prevent infection.

Prostaglandins

The typical next step in the induction process is to have synthetic prostaglandins inserted into your vagina in the form of a pessary or gel. These act like hormones and can help your cervix dilate and efface, which might bring on labor.

Artificial rupture of the membranes

If your cervix is ready for labor, your healthcare provider may offer to rupture your membranes. This involves using a small hooked instrument to break your amniotic sac. Sometimes this alone can be enough to start your contractions, meaning you wouldn’t need to progress to the next stage of induction.

There is an increased risk of infection, placental abruption, and umbilical prolapse. As with any procedure, you’ll need to weigh the risks and benefits with your healthcare providers and assess whether it’s the right course of action for you.

Synthetic oxytocin (Pitocin)

This will be used when all other methods have failed or aren’t suitable for you. It involves giving you synthetic oxytocin through an IV pump. Oxytocin is the natural hormone that your body produces during labor to stimulate contractions.

In most cases, women may need between 6 and 12 hours on a Pitocin drip to enter active labor. Usually, the drip will be started on the lowest dose and increased gradually until your contractions become regular. Contractions on a Pitocin drip are usually stronger and more painful than they would be naturally. There is no gentle build up to the contraction peak like you would get in a labor that started spontaneously. Instead, these contractions hit hard right at the beginning.

In 1964, Edward Bishop set forth criteria for elective induction of labor which included parity, gestational age, fetal presentation, obstetric history, and patient consent as well as a scoring system for the cervix to help predict successful induction of labor. This pelvic scoring system, widely known as the Bishop score, is still an important determination in the prediction of successful induction of labor. The pelvic score can be ascertained in a patient at the time of induction by a digital cervical exam to determine if cervical ripening is necessary before induction. This activity describes the Bishop score criteria and highlights the role of the interprofessional team in the management of a patient at the end of her pregnancy.

Objectives:

• Identify the criteria involved in the Bishop score.

• Describe the indications for use of the Bishop score.

• Review the clinical relevance of the Bishop score.

• Summarize the importance of the use of the Bishop score in improving care coordination among interprofessional team members to improve outcomes in patients awaiting labor and delivery.

In 1964, Edward Bishop set forth criteria for elective induction of labor which included parity, gestational age, fetal presentation, obstetric history, and patient consent as well as a scoring system for the cervix to help predict successful induction of labor. This pelvic scoring system, widely known as the Bishop score, is still an important determination in the prediction of successful induction of labor.  The pelvic score can be ascertained in a patient at the time of induction by a digital cervical exam to determine if cervical ripening is necessary before induction.[1][2][3]

The Bishop score reflects the normal changes the cervix undergoes in parturition (the process of childbirth). Extensive cervical remodeling is needed for the cervix to dilate and pass a fetus fully. While human parturition is not completely understood, it is a complex system that involves interactions between placental, fetal, and maternal mechanisms. The nonpregnant cervix extracellular matrix is primarily made up of tightly packed collagen bundles. Gradually throughout the pregnancy the composition of the cervix changes with decreased collagen density and an increase in hyaluronic acid and water content. In the days to weeks before delivery, through a cascade of events, inflammatory mediators increase the production of prostaglandins. Prostaglandins invading the cervix mediate the release of metalloproteases that break down collagen and change the cervical structure. Cervical softening and distention results from these extracellular matrix compositional changes, specifically, increased vascularity and stromal and glandular hypertrophy, and are due in part to an increase in collagen solubility.

The Bishop scoring system is based on a digital cervical exam of a patient with a zero point minimum and 13 point maximum. The scoring system utilizes cervical dilation, position, effacement, consistency of the cervix, and fetal station. Cervical dilation, effacement, and station are scored 0 to 3 points, while cervical position and consistency are scored 0 to 2 points (see chart below).[4][5][6]

• Cervical dilation is the measure of how dilated the cervix is in centimeters.  This is performed by estimating the average diameter of the open cervix.

• Effacement is the thinning or shortening of the cervix expressed as a percentage of the whole cervix.  Zero percent effacement means the cervix is a normal, pre-labor length. Fifty percent effaced means the cervix is at half of the expected length. If the cervix is 100% effaced, it is paper thin.

• The station is the position of the fetal head relative to the ischial spines of the maternal pelvis. The ischial spines are halfway between the pelvic inlet and outlet. At zero station, the fetal head is at the level of the ischial spines. Above and below this level are divided into thirds, by which station is denoted with negative numbers above and positive numbers below the zero station. As a fetal head makes its descent, the station changes from -3, -2, -1, 0, +1, +2, +3. In 1989, the American College of Obstetrics and Gynecology redefined station from -5 to +5, using centimeters instead of thirds as a measurement from the ischial spines. The Bishop score, however, uses the -3 to +3 system.

• Position refers to the position of the cervix relative to the fetal head and maternal pelvis.

• The consistency of the cervix refers to the feel of the cervix on the exam. A firm cervix has a consistency similar to the tip of the nose, while a soft cervix has a consistency similar to the lips of the oral cavity.

A Bishop score of 8 or greater is considered to be favorable for induction, or the chance of a vaginal delivery with induction is similar to spontaneous labor.  A score of 6 or less is considered to be unfavorable if an induction is indicated cervical ripening agents may be utilized.

The most common modification to the Bishop score is a simplified scoring system that just takes into account dilation, effacement, and station (each scored 0 to 3 points). In this shortened modification, a score of more than 5 is considered favorable.

Avoid digital cervical exams in a patient with placenta previa or before establishing a diagnosis of preterm rupture of membranes.

Induction of labor is a commonplace obstetric practice. Currently, more than 20% of pregnant women in the United States deliver as a result of labor. Predictors for success in induction include many of the similar criteria Bishop set forth in the 1960s. While, originally, the Bishop score was designed for multiparous patients, it applies to nulliparous patients undergoing induction as well. Increasing maternal parity is a strong indicator of the likelihood of successful vaginal delivery and a predictor of shorter length of labor. Fetal size, gestational age, maternal age, provider patience, and decision to induce versus expectantly manage can be correlated to differing success rates. Maternal body mass index can play a role as well, with the increased length of labor and cesarean delivery rates. The Bishop score is still widely in use to determine whether or not a cervix is “favorable” and to assess whether or not cervical ripening is needed. While Bishop score has been found to be useful for predicting vaginal delivery with sensitivity around 75% (similar between the full and modified scores) as well as a positive predictive value 83% to 84%, it has poor specificity and negative predictive value.

If a cervix is favorable, induction of labor is likely to result in vaginal delivery, and any method of induction tends to work well.  In the scenario of a favorable cervix, labor induction is normally undertaken with oxytocin and/or amniotomy.

If a cervix is considered to be unfavorable, no method is highly effective for induction so that patient is a candidate for cervical ripening. Cervical ripening is a process that helps prepare the cervix for labor and can result in a more favorable cervix. There are two main types of cervical ripening, prostaglandin use and mechanical methods.  Prostaglandins are a medication that can be given vaginally, buccally, or orally to a patient with an unscarred uterus that can help the cervix progress to a more favorable Bishop score in 12 to 24 hours. Mechanical methods such as a balloon catheter and hygroscopic dilators can be used as well. Mechanical methods, such as a balloon catheter, have shown to have similar outcomes to prostaglandins. Mechanical methods can be used in conjunction with prostaglandins in certain clinical scenarios. 

The bishop score is still an important determination in the prediction of successful induction of labor.  The pelvic score can be ascertained in a patient at the time of induction by a digital cervical exam to determine if cervical ripening is necessary before induction. The score is often performed by a labor and delivery nurse or an obstetrician. 

Review Questions

Bishop Scoring System. Contributed by Kelly Wormer, MD

1.

Hamm RF, Downes KL, Srinivas SK, Levine LD. Using the Probability of Cesarean from a Validated Cesarean Prediction Calculator to Predict Labor Length and Morbidity. Am J Perinatol. 2019 May;36(6):561-566. [PMC free article: PMC6491246] [PubMed: 30508870]

Coviello EM, Iqbal SN, Grantz KL, Huang CC, Landy HJ, Reddy UM. Early preterm preeclampsia outcomes by intended mode of delivery. Am J Obstet Gynecol. 2019 Jan;220(1):100.e1-100.e9. [PMC free article: PMC7605098] [PubMed: 30273585]

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Pez V, Deruelle P, Kyheng M, Boyon C, Clouqueur E, Garabedian C. [Cervical ripening and labor induction: Evaluation of single balloon catheter compared to double balloon catheter and dinoprostone insert]. Gynecol Obstet Fertil Senol. 2018 Jul - Aug;46(7-8):570-574. [PubMed: 29903553]

Keulen JKJ, Bruinsma A, Kortekaas JC, van Dillen J, van der Post JAM, de Miranda E. Timing induction of labour at 41 or 42 weeks? A closer look at time frames of comparison: A review. Midwifery. 2018 Nov;66:111-118. [PubMed: 30170263]

Lajusticia H, Martínez-Domínguez SJ, Pérez-Roncero GR, Chedraui P, Pérez-López FR., Health Outcomes and Systematic Analyses (HOUSSAY) Project. Single versus double-balloon catheters for the induction of labor of singleton pregnancies: a meta-analysis of randomized and quasi-randomized controlled trials. Arch Gynecol Obstet. 2018 May;297(5):1089-1100. [PubMed: 29445926]