A 36-yeаr-оld G3P2 wоmаn аt 41 weeks gestatiоn presents in active labor at 6 cm dilated with painful contractions occurring every 3 minutes. She reports that her "water broke" right before coming to the hospital. Past medical history is significant for COPD and type 2 diabetes mellitus. The patient is a supervisor at a post office and admits that she has been smoking more over the past two weeks due to stress from her job. The estimated fetal weight from her last appointment is 4600 g. She is admitted, and 2 hours later progresses to 8 cm and remains there for the next 4 hours. External fetal heart monitoring demonstrates a fetal heart rate of 103 beats/min. The patient is taken to the operating room for an emergent cesarean section. Which of the following factors is most likely responsible for the arrest of labor in this patient?