2026 Eastern States Conference

Title: Impact of documented beta-lactam allergy on surgical antimicrobial prophylaxis selection in cesarean delivery

Authors: Catherine Herman, PharmD; Corey Medler, PharmD, MPH, BCIDP; Lindsay Donohue, PharmD, BCIDP 

Learning Objective: At the conclusion of my presentation, audience members will be able to describe how β-lactam allergy documentation can influence surgical antimicrobial prophylaxis (SAP) choice and timing in cesarean deliveries. 

Background/Objective: Although cefazolin’s unique R-1 side chain makes cross-reactivity with other β-lactams rare, this study evaluates whether documented β-lactam allergy affects SAP choice and timing in cesarean deliveries. 

Methods: This single-center, retrospective, cross-sectional study included adult patients (≥ 18 years) who underwent cesarean delivery at a large academic medical center in central Virginia from June 1, 2024 to May 31, 2025. Patients receiving antibiotics for treatment of active infection were excluded. The primary endpoint was the percentage of patients with a documented β-lactam allergy who received inappropriate SAP, encompassing both agent selection and timing. Secondary endpoints included inappropriate SAP amongst all cesarean delivery patients, incidence of suspected surgical site infection (SSI), postoperative acute kidney injury (AKI), and Clostridioides difficile infection (CDI). Data were collected through manual electronic medical record review and analyzed using descriptive statistics, chi-square, and Fisher’s exact tests. 

Results: Of 208 patients included, 104 had a documented β-lactam allergy and 104 did not. Most documented allergens were penicillins (>80%); 2 patients reported a cefazolin allergy. IgE-mediated reactions were most common (46%), followed by mild reactions (41%). Inappropriate SAP occurred in 22.1% of patients with a documented β-lactam allergy vs. 11.5% in non-β-lactam allergy patients (OR 2.18, p = 0.041). This was driven by higher rates of inappropriate agent selection (14.4% vs. 1.9%; OR 8.60, p = 0.001) and timing (21.2% vs. 10.6%; OR 2.27, p = 0.037) in β-lactam allergy patients. Suspected SSI occurred in 6.7% of patients, with no significant difference by allergy status or agent appropriateness. No postoperative AKI or CDI were identified. 

Conclusions: Documented β-lactam allergy was associated with a higher rate of inappropriate SAP selection and timing, driven largely by unnecessary avoidance of cefazolin. These findings highlight opportunities for β-lactam allergy evaluation and de-labeling, optimization of perioperative order sets, and integration of decision-support tools to improve antimicrobial stewardship in cesarean deliveries. 

Self-Assessment Question: True/False: A documented β-lactam allergy was associated with significantly higher odds of inappropriate SAP, even though most patients could have safely received cefazolin.