Safety of Cefazolin in Pregnant Patients with Documented Penicillin Allergy: A Retrospective Cohort Study.

Background: The antibiotic cefazolin is commonly used in pregnancy, as first-line prophylaxis for cesarean section wounds or as an alternative to penicillin for prophylaxis against group B Streptococcus. About 10% of people report a penicillin allergy, and clinicians have historically avoided the use of β-lactams (including cefazolin) in these individuals. Instead, they have used non-β-lactams, which can lead to poorer maternal outcomes.

Objective: To evaluate the safety of cefazolin in pregnant patients with a documented history of penicillin allergy.

Methods: This retrospective cohort study included all pregnant patients with a documented penicillin allergy at the time of receiving their first dose of cefazolin at a large tertiary care hospital (January 2016 to August 2021). Descriptive statistics were calculated.

Results: A total of 179 patients were included in the analysis. Most (175 [97.8%]) had no allergic adverse event after receiving cefazolin. Two patients (1.1%) experienced immunoglobulin E (IgE)-mediated hives, and 2 patients (1.1%) experienced non-IgE-mediated rashes. No patients experienced anaphylaxis, and no patients with a documented history of anaphylaxis to penicillins experienced an allergic adverse event related to cefazolin. All 4 patients who experienced an allergic adverse event were discharged with no readmission to the study institution associated with the allergic adverse event.

Conclusion: No patients with a documented history of anaphylaxis to penicillin experienced an allergic adverse event upon receiving cefazolin. Cefazolin was safely given to pregnant people with a history of penicillin allergy.