Obstetric surgical site infections: 2 grams compared with 3 grams of cefazolin in morbidly obese women

OBJECTIVE: To estimate whether morbidly obese gravid patients were less likely to develop a surgical site infection after receiving a higher dose of preoperative prophylactic antibiotics. METHODS: A retrospective cohort study of morbidly obese pregnant women undergoing cesarean delivery was conducted at two tertiary care centers from 2008 to 2013. Exposure was defined as receiving 2 g compared with 3 g cefazolin preoperatively. Disease was defined by diagnosis of a surgical site infection using Centers for Disease Control and Prevention criteria. We estimated a sample size of 141 patients in each group for a 67% reduction (15% to 5%) in risk for a surgical site infection. RESULTS: There were 335 women included in the cohort with a median absolute weight of 310 (interquartile range 299-333) pounds. Forty-four (13.1%) women were diagnosed with a surgical site infection. There was no difference in surgical site infection among those women who received 2 g compared with 3 g cefazolin (13.1% [23/175] compared with 13.1% [21/160]; P5.996). Labor (crude odds ratio [OR] 2.31, 95% confidence interval [CI] 1.21-4.40), internal labor monitoring (OR 2.78, 1.45-5.31), blood loss greater than 1,500 mL (OR 2.15, 1.09-5.78), and staple closure (OR 2.2, 1.15-4.21) were associated with a surgical site infection among the entire cohort. After multivariable analysis, blood loss greater than 1,500 mL (adjusted OR 3.32, 1.32-8.37) and staple closure (adjusted OR 2.45, 1.19-5.02) remained associated with an increased risk for a surgical site infection, whereas 3 g cefazolin still was not associated with reduced risk for a surgical site infection (adjusted OR 1.33, 0.64-2.74). CONCLUSION: In our multicenter retrospective cohort study, preoperative 3 g cefazolin prophylaxis administered to morbidly obese gravid patients did not reduce surgical site infections.