OBJECTIVE: To determine whether chlorhexidine vaginal irrigation prevents maternal puerperal infection. STUDY DESIGN: Double-blinded, placebo-controlled, randomized trial. Intervention: Single 200 rr irrigation of either 0.2% chlorhexidine (C) solution or sterile water placebo (P) in active labor or prior to planned cesarean. Pre-trial in vitro testing confirmed broad antibacterial action of C but not P solution. Priman outcome measure: the combined rate oi cborioaninioniiis and endometritis (which were mutually exclusive diagnoses). RESULTS: 1,02-1 patients uere enrolled: 508 C. 510 P. The two groups were generally well-balanced on important clinical factors including maternal weighl. race, gestational age. birthweight, duration of ruptured membranes, irrigation to deliver) interval, rates of spontaneous labor, vaginal deliver, and epidural usage. The groups differed (P < 0.0.05) in rates of nulliparitv (C 42%. P 52%). IIJPC usage (C 65%, P 72%), and presence of mecoiiium (C 17%.. P 22%). Then1 were no recognized adverse maternal or neonatal irrigation reactions. Rales of infection (chorioamnionitis + endometritis) did not differ between the groups, C 10% vs. P 13% (RR 0.8, 95% CI 0.5-1.1). Stratified (e.g.. paritv. deliver) tvpe, IUPC tise, meeonium ±. irrigation pre/post ROM. duration of membrane rupture > median) and logistic regression analvses supported the primary univariate analvsis. Neonatal outcomes, including sepsis rates of 0.4%, were equivalent for the gioups. The study power was >90% to deteci a 50% difference in the piimarv outcome. CONCLUSIONS: As uuli/ed in this trial, chlorhexidine lacked efficacy in the prevention of maternal puerperal infection.