Study of Effectiveness and Safety of Azithromycin-based Extended-spectrum Prophylaxis to Prevent Post Cesarean Infection

Inclusion Criteria: \- Pregnant Women aged 14 years and over at ≥ 24 weeks' viable gestation who will undergo unscheduled/non-elective cesareans with either: 1. Labor (spontaneous or induced): active labor (ongoing contractions and at least 4cm dilated or contractions for at least 4 hours with documented cervical change of ≥1cm dilatation or ≥50% effacement), or 2. Membrane rupture (standardized to duration of at least 4 hours prior to randomization). Exclusion Criteria: * Patient unwilling or unable to provide consent * Multiple pregnancy * Known azithromycin (or other macrolide) allergy * Vaginal delivery * Elective or scheduled cesarean prior to labor or membrane rupture. * Azithromycin, erythromycin or other macrolide antibiotic use within 7 days of enrollment. * Clinical chorioamnionitis or any other active bacterial infection (e.g. pyelonephritis, pneumonia, abscess) at time of randomization. * Patient is unable or unlikely to follow-up after delivery (e.g. no prenatal care or a non-resident patient) * Fetal demise or major congenital anomaly * Significant liver disease defined as known cirrhosis or elevated transaminases of at least 3-fold upper limit of normal * Significant renal disease defined as serum creatinine known to be \>2.0 mg/dl or on dialysis. * Active congestive heart failure (EF\<45%) or pulmonary edema * Active diarrhea at time of delivery * Any patient with significant electrolyte abnormalities such as hypokalemia or hypocalcemia * Any patient with structural heart disease or arrhythmias, or taking any medications known to prolong the QT interval * Patient currently being treated with efavirenz, nelfinavir or fluconazole