Azithromycin pretreatment lowers infection rate after C-section, NIH-funded study finds

Pregnant woman in hospital bed.

Treatment with the antibiotic azithromycin before an unplanned cesarean delivery reduces the post-operation infection rate by about 50 percent, compared to the standard treatment, according to a study funded by the National Institutes of Health. Results of the study appear in the September 29 issue of the New England Journal of Medicine.

Roughly 60 to 70 percent of all cesarean deliveries are unplanned, the study authors wrote.  Despite the standard pretreatment with the antibiotic cephalosporin, about 12 percent of women who have an unplanned cesarean delivery develop an infection after the surgery. The authors add that infection is the fourth most common cause of pregnancy-related death in the United States.

The researchers studied more than 2,000 pregnant women at 14 centers in the United States. All were in the 24th week of pregnancy or later and were undergoing a cesarean section. Roughly half the women were assigned at random to receive 500mg of intravenous azithromycin before the surgery; the other half received a placebo. All then received the standard treatment of cephalosporin. Among the women who received azithromycin, 6.1 percent had an infection after surgery. Among the placebo group, 12 percent had an infection. There were no differences in the rate of complications among newborns in the two groups.

Tita, ATN, et al. “Adjunctive azithromycin prophylaxis for cesarean delivery.” N Engl J Med 2016; 375:1231-1241 September 29, 2016 External Web Site Policy. DOI: 10.1056/NEJMoa1602044


About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): NICHD conducts and supports research in the United States and throughout the world on fetal, infant and child development; maternal, child and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit NICHD’s website.

About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit

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