Management of Active Phase Arrest
In order to manage active phase arrest, the active phase must be correctly defined, and arrest properly diagnosed. The active phase begins when there is an acceleration in the rate of cervical dilation. Friedman proposed that this period began after achieving 4 cm of cervical dilation. More recent studies that incorporate modern labor management practices support defining the active phase as beginning at 6 cm of cervical dilation.
In response to the high rate of cesarean delivery in the United States, the Safe Labor Consortium was formed to evaluate contemporary labor progression. The Safe Labor Consortium redefined arrest of the active phase of labor as occurring at 6 cm or more, with the amniotic membranes ruptured, and no cervical change after either:
- 4 hours of adequate contractions
- 6 hours of inadequate contractions despite oxytocin administration.
Cesarean delivery for arrest of the active phase should not be performed before the above criteria are met, as long as maternal and fetal status are reassuring. The presence of meconium stained amniotic fluid does not change these recommendations.
Inadequate uterine contractions are the most common cause of active phase arrest, followed by fetal malpresentation, and less frequently, cephalopelvic disproportion.
When there is concern that cervical change has stopped or slowed, amniotomy and oxytocin augmentation may be employed. Amniotomy should be performed if the fetal membranes are intact. If the contraction pattern is abnormal, the first line therapy is intravenous oxytocin. Low and high dose protocols have been studied but neither has been proven to be superior to the other. The combination of oxytocin and amniotomy has been shown to be more effective than either modality alone.
Internal tocodynamometry using an intrauterine pressure catheter (IUPC) should be considered when there is no progress despite a normal contraction pattern and/or oxytocin administration. The IUPC can be used to quantify the magnitude of contractions in Montevideo units. A contraction pattern is considered adequate when the sum of the Montevideo units from all contractions in a 10-minute period is greater than or equal to 200. If the Montevideo units are less than 200, the oxytocin infusion rate may need to be titrated to increase the frequency and/or magnitude of contractions. An IUPC may also be helpful when maternal body habitus or other factors preclude accurate assessment of the contraction pattern using an external monitor.
If these efforts fail and active phase arrest is diagnosed, cesarean delivery should be recommended. Prolonged labor and rupture of membranes are risk factors for maternal and neonatal infection, and prolonged labor and oxytocin administration are risk factors for postpartum hemorrhage. However, studies have demonstrated that following this management strategy decreases the rate of cesarean delivery without worsening maternal or neonatal outcomes.
Initial Approval July 2019
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This document is designed to aid practitioners in providing appropriate obstetric and gynecologic care. Recommendations are derived from major society guidelines and high quality evidence when available, supplemented by the opinion of the author and editorial board when necessary. It should not be construed as dictating an exclusive course of treatment or procedure to be followed.
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