SOURCES: William Andrews, Ph.D., M.D., professor and chairman, department of obstetrics and gynecology, University of Alabama at Birmingham; Robert Weinstein, M.D., professor, internal medicine, Rush Medical College, Chicago; Sept. 29, 2016, New England Journal of Medicine
THURSDAY, Sept. 29, 2016 (HealthDay News) -- Doctors routinely give an antibiotic before a cesarean-section, the surgical delivery of a baby, to prevent infection in the mother. But, a new study suggests that adding a second antibiotic can cut the risk of infection even more.
The researchers found that adding azithromycin to standard antibiotic therapy cut infection rates by 50 percent.
"A simple approach involving the addition of a single dose of azithromycin, a relatively inexpensive and readily available antibiotic, to the recommended standard dose of a single antibiotic such as cefazolin is associated with a markedly lower rate of post-cesarean infection," said senior researcher Dr. William Andrews. He's chairman of the department of obstetrics and gynecology at the University of Alabama at Birmingham.
Cesarean delivery is the most common major surgical procedure performed in the United States. Sixty to 70 percent of these are non-elective, often occurring during labor or because of ruptured membranes, Andrews said.
Infection is arguably the most common complication of a cesarean delivery, he noted.
Infection risk is about five to 10 times higher after a cesarean delivery compared with a vaginal delivery, Andrews said. Overall, about 12 percent of C-sections result in an infection, according to background information in the study. That's about one in eight women who undergo the procedure.
"These infections represent the most common complication. And they are associated with considerable expense, discomfort, occasionally even maternal death," he said.
More than 2,000 women were recruited for the study. All were having a non-elective cesarean delivery and received the standard antibiotic therapy. About half were randomly assigned to also receive azithromycin. The rest were given an inactive placebo.
The researchers looked for infections occurring within six weeks after delivery.
"Compared to the group receiving the standard antibiotic plus a placebo, the overall rate of infection was 50 percent lower in the group receiving the standard antibiotic plus the second antibiotic, azithromycin," Andrews said.
Over the study period, 6 percent of the women who received azithromycin developed an infection, compared with 12 percent of the women who received the placebo, the findings showed.
Endometritis -- an infection of the lining of the uterus -- occurred in 4 percent of the women given azithromycin, compared with 6 percent of those given a placebo, the study found.
In addition, just over 2 percent of women given azithromycin developed infections at the site of the surgical incision, compared to nearly 7 percent of those given a placebo.
One health expert said a variety of factors may account for these findings.
"Azithromycin may kill bacteria not covered by cefazolin," said Dr. Robert Weinstein. He's a professor of internal medicine at Rush Medical College in Chicago.
Also, azithromycin may increase the amount of antibiotics in obese patients who are not receiving enough cefazolin, he suggested.
"Based on these results, many women undergoing a C-section would receive broader antibiotics before delivery," Weinstein said.
"In light of the number of C-sections in the U.S. each year, this could impact a large number of deliveries," he added.
The report was published in the Sept. 29 issue of the New England Journal of Medicine.
For more on cesarean delivery, visit the U.S. National Institute of Child Health and Human Development.