LAS VEGAS – Two days of prophylaxis with two oral antibiotics cut the surgical site infection rate by more than half in a randomized trial with more than 400 obese women who had cesarean deliveries.
The protective effect from combined treatment with cephalexin and metronidazole was especially powerful in the most at-risk patients, women with ruptured membranes before cesarean surgery. In this subgroup prophylaxis with the two antibiotics for 2 days cut surgical site infections (SSIs) during the 30 days after surgery, from a rate of 33% in control women who received placebo to a 10% rate, a 77% relative risk reduction that was statistically significant,, said at the annual Pregnancy Meeting sponsored by the Society for Maternal and Fetal Medicine.
“I am very excited that we found a way to help the kinds of women in the study, very-high-risk women, with an effective way to reduce their risk of infection,” Dr. Warshak of the University of Cincinnati said in a. The obese women enrolled in the study, especially those with ruptured membranes, “have a very high risk of morbidity, so it’s very exciting that we found a way to help prevent” SSIs.
“Our study is the first to target postpartum interventions to reduce SSIs specifically in this high-risk population” of obese mothers, said, a maternal fetal medicine clinician at Oregon Health & Science University in Portland, who ran the trial with Dr. Warshak.
The trial randomized women with a body mass index of at least 30 kg/m2 who underwent a planned or unplanned cesarean delivery at the University of Cincinnati during 2010-2015. Following standard management during cesarean delivery, the women received either 500 mg oral cephalexin and 500 mg oral metronidazole or placebo every 8 hours for 48 hours following delivery. The primary outcome was the incidence of SSIs, and randomization was stratified so that similar numbers of women with ruptured membranes got into each treatment arm. The enrolled women averaged 28 years of age, and average BMI was about 40 kg/m2. Nearly a third of the women had ruptured membranes at the time of surgery, more than a quarter of the enrolled women used tobacco, and more than a fifth had preeclampsia.
Additional analyses reported at the meeting by Dr. Valent showed that other risk factors that significantly boosted the rate of SSIs were labor prior to delivery, use of internal monitoring, and operative time of more than 90 minutes. Antibiotic prophylaxis was able to significantly reduce SSI rates in women with any of these additional risk factors, compared with placebo. A cost effectiveness analysis she ran estimated that if the antibiotic prophylaxis tested in the study were used on the roughly 460,000 obese U.S. women having cesarean deliveries annually, it would be cost saving as long as the antibiotic regimen cost no more than $357 a person. Factoring in the SSIs and long-term morbidity that prophylaxis would prevent, and the quality-adjusted life-years it would add, showed that prophylaxis would be cost-effective up to a cost of $33,557 per woman.
The prophylaxis carries a “relatively low cost and is easy to use,” Dr. Valent said.
Safety of the antibiotic combination was a question raised by, director of ob.gyn. infectious disease and labor and delivery at Massachusetts General Hospital in Boston. “My biggest concern is 48 hours of these antibiotics,” and whether prophylaxis could be achieved with fewer doses, she said in an interview. “I’d want to minimize the dosage, and also try other, nondrug approaches to minimizing SSI risk in obese women.”
“I wouldn’t say that universally, every obstetrical program should do this, but clinicians should look at the comorbidities their mothers have and their SSI rates. There are populations out there at lower risk, but there are also populations like ours, with a SSI rate of 10%-20%,” Dr. Warshak said.
She also acknowledged that even her own obstetrical group in Cincinnati needs to now reach a consensus on an appropriate strategy for expanded cesarean-delivery prophylaxis. That’s because a 2016 report from a large, randomized trial documented another successful strategy for limiting infections following cesarean delivery: a preoperative intravenous dose of azithromycin as a supplement to standard cefazolin. The Cesarean Section Optimal Antibiotic Prophylaxis () trial, done in women with any BMI but specifically nonelective cesarean deliveries, showed a significant reduction in the combined rate of SSIs, endometritis, or any other infection during 6 weeks of follow-up among women who received azithromycin on top of standard prophylaxis ( ).
“The bottom line is that, a couple of grams of cefazolin [administered before the incision] isn’t enough, especially for women with risk factors for infection. We see infection rates of more than 10% because cefazolin alone is simply inadequate. The results from both our study and the 2016 study show we can do better to reduce morbidity,” said Dr. Warshak.
“In high-risk women, such as those who are obese, we probably need to expand the spectrum and duration of prophylaxis,” agreed Dr. Main. “Obesity is one high-risk group, but there are others.”