ATLANTA – Preincisional azithromycin reduced postcesarean maternal infections by half, and significantly cut postpartum trips to the hospital.
Given in tandem with standard prophylactic antibiotics, broad-spectrum intravenous azithromycin was highly effective, with a number needed to treat of 17 to prevent one postsurgical infection, and 43 to prevent one case of endometritis, Dr. Alan Tita reported at the annual Pregnancy Meeting sponsored by the Society for Maternal-Fetal Medicine.
Dr. Alan Tita
“We also saw fewer maternal adverse events, and the protocol was safe for the newborn,” said Dr. Tita, a professor of obstetrics and gynecology at the University of Alabama, Birmingham.
The Study of Effectiveness and Safety of Azithromycin-Based Extended-Spectrum Prophylaxis to Prevent Post Cesarean Infection (C/SOAP) trial enrolled 2,013 women at 14 sites. All patients had singleton pregnancies of at least 24 weeks’ gestation. Patients had a cesarean after at least 4 hours of active labor or 4 hours after rupture of membranes.
All women received standard narrow-spectrum antibiotic prophylaxis with either cefazolin or clindamycin. They were randomized to either preincisional intravenous azithromycin 500 mg or saline placebo. The study had a pragmatic design, so skin disinfection was performed according to each facility’s standard protocol.
The primary outcome was a composite of endometritis, wound infection, abscess, pelvic septic thrombophlebitis, pyelonephritis, pneumonia, and meningitis. Secondary outcomes were maternal fever, unscheduled visits to health care providers (including hospital readmissions and emergency department visits), and death.
The neonatal outcome was a composite of death; primary or suspected sepsis; and serious neonatal morbidities, including respiratory distress syndrome, necrotizing enterocolitis, periventricular leukomalacia, intraventricular hemorrhage of grade 3 or higher, and bronchopulmonary dysplasia.
There were no baseline differences in the indication for cesarean or type of skin and uterine incision, Dr. Tita said. Most patients (88%) received their study drug before the incision.
The rate of the primary composite outcome was reduced by half in women who had azithromycin added to their cephalosporin prophylaxis (6% vs. 12%; relative risk, 0.49). Wound infection was cut by 65% (2.4% vs. 6.6%; RR, 0.35).
Azithromycin significantly improved the secondary maternal outcomes over placebo, including fever (5% vs. 8.2%; RR, 0.61), and readmissions or unscheduled visits (8.2% vs. 12.4%; RR, 0.66). The addition of azithromycin was associated with a significant decrease in the rate of severe maternal adverse events (1.5% vs. 2.9%).
Study site, obesity, and the type of skin prep did not significantly affect any of these outcomes, Dr. Tita noted.
The addition of azithromycin was safe for neonates. The composite neonatal safety outcome occurred in 14.3% of the treated group and 13.6% of the placebo group – not a significant difference. There were no differences in suspected or confirmed sepsis (11.8% vs. 12.5%), serious neonatal morbidities (4.4% vs. 3.4%), or NICU admission (16.8% vs. 17%), Dr. Tita reported.
There were no deaths in either mothers or infants. There were 11 maternal allergic reactions, five admissions to intensive care, and five suspected cardiac events.
When asked whether even brief systemic exposure to azithromycin could alter the fetal microbiome, Dr. Tita said he shares that concern but the answer is still unknown.
“We have collected additional information and specimens and we will be looking at these to try and answer this. We also hope to get funding to do a long-term evaluation of these kids. I will say that we collected adverse event data on them for 3 months and we did not see anything concerning, but I agree more needs to be done,” he said. “Having said that, azithromycin is something we already use quite a lot in obstetrics, and overall it has been shown to be safe for the newborn.”
The study was sponsored by the National Institute of Child Health and Human Development. Dr. Tita reported having no financial disclosures.