Antibiotics before the cut, not after
Timing matters, and so does a second antibiotic in labor.
Antibiotics given before the skin incision rather than after the cord is clamped reduce infection substantially. In a review of 10 trials and 5,041 women, pre-incision antibiotics reduced overall maternal infection (relative risk 0.57), uterine infection (relative risk 0.54) and wound infection (relative risk 0.59), with no increase in newborn sepsis. That review reports these as proportional reductions and does not give pooled absolute rates, so read them as a fraction taken off whatever your own hospital's baseline infection rate is.
For a cesarean performed during labor or after membranes rupture, adding azithromycin cuts infection roughly in half. In a randomized trial of 2,013 women, infection occurred in 6.1% with azithromycin and 12.0% with placebo.
Chlorhexidine skin preparation lowers wound infection compared with iodine: 4.0% versus 7.3% in a randomized trial of 1,147 women.