Penicillin allergy assessment in pregnancy is safe, improves antibiotic choices

Published online: March 1, 2021

Although 32 million Americans report a penicillin allergy, the vast majority (over 95%) are not truly penicillin allergic. This can impact patients’ medical care in important ways because penicillins are first-line antibiotics known to be safe and effective for treatment of many infections. When penicillin is not an option, alternative antibiotics, which have more side effects and can be less effective, are used. In pregnancy, penicillin is even more important because it is safe for the growing baby and effective at treating infections which commonly affect pregnant women. A potentially dangerous infection called Group B Streptococcus (GBS), which can cause severe infections in the newborn, is best prevented by treatment with penicillin. A penicillin-related antibiotic (cefazolin) is the best choice preceding Caesarean sections (C-sections), which occur for about one-third of pregnancies. Testing to evaluate for penicillin allergy is generally safe and is performed in an Allergy Clinic with skin testing followed by administration of a dose of the antibiotic. Previously, it was unclear if doing this testing during pregnancy was safe, but since using alternative antibiotics has been associated with higher rates of adverse outcomes, the American College of Obstetrics and Gynecology recommended proceeding with penicillin allergy testing during pregnancy.  

In order to assess the safety and importance of evaluating for penicillin allergy in pregnancy, allergists at the Massachusetts General Hospital implemented a system in which obstetricians could request an electronic consultation from an allergist as to whether a patient would be a good candidate for penicillin allergy evaluation. Patients whose penicillin reaction occurred more than 5 years ago and had a less severe history were scheduled for an in-person evaluation in the Allergy Clinic. For patients with more severe or recent reactions, a recommendation to continue to avoid penicillin was placed in the electronic chart.

In the manuscript by Wolfson et al, published in The Journal of Allergy and Clinical Immunology: In Practice, retrospective data were collected on patients seen during the time period from September 2017 through December 31, 2019. The data focused on the pre-existing conditions affecting the pregnant women, whether they had GBS, whether they underwent a C-section delivery, any antibiotic-related allergic reactions, and antibiotics used (from pregnancy through 6 weeks post-delivery). The pregnant women were divided into two main groups for comparisons: those who were advised to undergo in-person penicillin allergy evaluation but did not and those who were seen in-person by Allergy.

Of almost 400 obstetric patients with listed penicillin allergies for whom an electronic consult was placed, 222 (61%) patients received in-person Allergy evaluation, whereas 141 (39%) patients were advised to be seen, but not seen in-person, most often for unknown reasons. Among the 222 patients evaluated in the Allergy Clinic, 209 (95%) had negative penicillin allergy test results, meaning that they were not allergic to penicillin. This testing was safe, with only 3 patients experiencing mild rashes after taking the oral penicillin and with no impact on timing of delivery or rate of C-section. In both groups, 60% of the women required antibiotics while they were pregnant or immediately after delivery. Compared with the patients who were recommended for Allergy evaluation but did not complete evaluation, those who were evaluated had significant changes to antibiotic selection, such as 17-fold lower odds of vancomycin use, 6-fold lower odds of clindamycin use, and more than 2.5-fold lower odds of gentamicin use. Penicillin was 18-fold more likely to be used in general, with penicillin use increased 27-fold as the first-line, preferred drug for GBS. Cefazolin preceding C-section was used twice as often in the group that had been evaluated. This study, which was at least 2 times bigger than the previously published studies on this topic, shows that, in collaboration with obstetricians, allergists should identify safe, feasible methods to evaluate pregnant patients with penicillin allergy histories to optimize antibiotic use in the peripartum period.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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