A 29-year-old gravida 2 para 1-0-0-1 female at 39 weeks’ gestation is admitted to the hospital in labor. Her pregnancy has been uneventful to date and all prenatal testing has been normal. Her first delivery was an elective cesarean section secondary to a breech presentation. On admission, her cervix is noted to be 4 cm dilated and 100% effaced, with the fetal vertex at 0 station. Contractions are every three minutes lasting 60 to 90 seconds. Fetal heart rate is 140/min and reactive. No decelerations are noted. Membranes are artificially ruptured and amniotic fluid is clear. Four hours later, her cervix is completely dilated, and she begins pushing. After 1 hour and 10 minutes of pushing, the vertex is at +2 station, and the baby is in a left occiput anterior position. The most likely diagnosis is