••• Chapter 5^ Labor and Delivery^55
❍ What is considered a favorable Bishop score?
≥9.
❍ What is considered an unfavorable Bishop score?
Four or less is considered unfavorable.
❍ How are dilatation and effacement defined?
Dilatation is defined in centimeters. Effacement is defined in percentages and refers to the thinning of the cervix.
❍ How frequently is the fetus vertex at term?
95% of all patients at term present as vertex.
❍ What do the cardinal mechanisms of labor refer to?
They refer to the changes in the position of the fetal head as it passes though the birth canal.
❍ Why does the fetal head need to change position at this time?
These changes are needed secondary to the asymmetric shape of the fetal head and maternal bony pelvis.
❍ How are these changes accomplished?
The changes occur as the result of the propulsive forces of uterine activity during labor.
❍ How many changes occur during the cardinal movements?
Seven.
❍ Name the cardinal movements of labor.
Engagement, descent, flexion, internal rotation, extension, external rotation, and expulsion.
❍ How is engagement defined?
Engagement occurs when the descent of the biparietal diameter (BPD) is below the level of the pelvic inlet.
❍ What is the average distance between the pelvic inlet and the ischial spines?
The average distance is 5 cm.
❍ When does the greatest rate of descent occur?
It most often occurs during the deceleration phase of the first stage of labor and during the second stage of labor.
❍ How does flexion usually occur?
Flexion usually occurs as a passive motion.
❍ Approximately what percentage of pregnant patients have factors that can be identified prenatally that place
the patient at increased risk?
Approximately 20% of patients have identifiable risk factors.