A 26-year-old G1P0 at 40w1d presents in spontaneous labor and is dilated to 4 cm. The patient reached complete cervical dilation after artificial rupture of membranes and oxytocin augmentation. After 4 hours of pushing, there has been minimal descent of the fetal vertex beyond +1 station with significant caput succedaneum. Her physician decides to proceed with cesarean delivery. What antibiotics should be administered prior to incision to reduce postoperative infection?