Identify risk factors for postpartum readmission in class 3 obese patients undergoing unscheduled cesarean deliveries. Retrospective cohort study of patients with BMI ≥ 40 kg/m2 undergoing unscheduled cesarean delivery from 2017-2020 comparing patients with and without postpartum readmission (unexpected admission, emergency room/overnight observation visit, unscheduled outpatient visit, or ambulatory surgery within 30 days). Medical history, operative data, and postpartum outcomes were compared between the cohorts. "The electronic medical record was queried to identify cesarean deliveries documented as 'unscheduled'". 255 of 1273 identified patients (20.0%) had a postpartum readmission. Median BMI was similar between the cohorts (44.2 kg/m2, IQR [41.8, 47.9] vs. 44.8 kg/m2 [42.0, 48.9], p= 0.066). Readmitted patients were more likely to have a history of smoking during or prior to pregnancy (p= 0.046). A sub-group exploratory analysis excluding outpatient and emergency room visits demonstrated higher rates of type II diabetes mellitus in patient's with postpartum readmission (11.5% vs 4.6%, p= 0.030). Patients with readmission in comparison to those without readmissions were less likely to receive cefazolin prophylaxis (78.0% vs 84.3%, p= 0.014) in comparison to gentamicin/clindamycin prophylaxis. Patients with readmission were less likely to have had vaginal preparation (56.9% vs 64.3%, p= 0.027). On multivariable logistic regression analysis, smoking history (OR 1.44, 95% CI 1.06-1.96, p= 0.0220) and hypertensive disease (OR 1.57, 95% CI 1.18-2.09, p 0.002) were associated with readmission. Cefazolin preoperative prophylaxis (OR 0.59, 95% CI 0.41-0.84, p= 0.004) and vaginal sterile preparation (OR 0.72, 95% CI 0.54- 0.95, p= 0.022) were associated with decreased risk of readmission. In class 3 obese patients, a history of smoking and a diagnosis of hypertensive disease associate with increased risk of postpartum readmission. Perioperative antibiotic prophylaxis with cefazolin along with vaginal sterile preparation associate with decreased risk of postpartum readmission.