••• Chapter 10^ Labor Abnormalities^99
❍ Complete the table, indicating the criteria for second-stage arrest in nulliparas and multiparas.
No regional anesthesia regional anesthesia
Nullipara ________ hours ________ hours
Multipara ________ hours ________ hoursNo regional anesthesia regional anesthesia
Nullipara 3 hours 4 hours
Multipara 2 hour 3 hours❍ The most commonly used unit of uterine activity is?
The Montevideo unit.
❍ A Montevideo unit is defined as?
Peak of contractions in millimeters of mercury minus baseline uterine pressure multiplied by the frequency of
contractions per 10-minute period.
❍ Can Montevideo units be calculated based on the contractions depicted from the traditional external
tocodynamometry?
No. The external monitoring can determine length and frequency of contractions, but not their strength. An
intrauterine pressure catheter must be used to calculate Montevideo units, and can be placed after rupture of
membranes has occurred.
❍ Traditionally, what two criteria must be met to diagnose an arrest disorder in the first stage of labor?
(1) At least 6 cm dilated.
(2) Uterine contraction pattern exceeding 200 Montevideo units for at least 4 hours without cervical change
calculated using an intrauterine pressure catheter.
❍ True or False: In making the diagnosis of active phase arrest, 4 hours of sustained uterine contractions without
cervical change may be more appropriate than the traditional “2-hour rule.”
True.
❍ Are the cut-off time as listed above for second-stage arrest absolute?
No. If the fetal heart tracings are reassuring, there have been no excess findings of neonatal morbidity associated
with a prolonged second stage. If there is steady progress, there is no need to conform to these cut-offs.