INTRODUCTION: Surgical site infections (SSI) are common complications following cesarean delivery. As part of a performance improvement project, we recognized the need to differentiate infections based on severity and thus sought to characterize the most severe cases of SSI. METHODS: We performed a retrospective review of women ≥18 years or older who delivered by cesarean in 2016 and 2017 at a Women's Hospital. Using a combination of ICD-10 diagnosis codes, the electronic medical record, and infection control surveillance, we identified cases and confirmed all diagnoses by chart review using CDC definitions for SSI. We defined severe SSI as cases requiring additional treatment (change in antibiotics or additional procedure), readmission, CT imaging, ICU admission, or length of stay ≥7 days. We compared maternal demographics and clinical characteristics between severe and non-severe cases using the Student t-test and Fischer exact test as appropriate. RESULTS: Among 3,507 cesarean deliveries, 141 met criteria for SSI. Of these, there were 53 cases of severe SSI. Women with severe SSI were older (31.9 vs. 30.2 years, p=0.01), had lower gestational ages at delivery (35.8 vs. 37.6 weeks, p<0.01), were more likely to have diabetes (26.4% vs. 10.2%, p=0.02) and less likely to have endometritis only (50.9% vs. 81.8%, p<0.01). There was no difference between groups in BMI, prior cesarean, hypertension, GBS status, length of labor or rupture of membranes, or emergent/urgent deliveries. CONCLUSION: In our cohort, severe SSI was associated with older age, diabetes, and earlier deliveries. Further research is needed to identify modifiable risk factors and guide prevention strategies.