Penicillin skin testing – how safe in pregnant women?

Penicillin skin testing in pregnant women is safe both for the mum and the baby, experts assure at AAAAI 2021.

The American College of Obstetricians and Gynecologists in 2019 advocated that women who have a penicillin-allergy label get an allergy evaluation before or during pregnancy, given that penicillin is first-line for the prevention of group B streptococcus (GBS) infection in women and their babies, said study author Dr Vima Patel from the University of Pennsylvania Perelman School of Medicine in Philadelphia, US.

“Despite the recommendation, allergists were still hesitant to perform penicillin allergy testing in pregnant women,” she shared during her virtual talk at AAAAI 2021. “Obstetricians weren’t always referring these women for evaluation.”

GBS in pregnant women can cause infection of the urinary tract, placenta, womb, and even the amniotic fluid. If undetected, women can pass the infection to their babies during labour and delivery.

A retrospective review of a cohort of 122 pregnant women who were referred to an allergy clinic by their obstetrician showed that of the 119 women who underwent skin testing, 115 turned negative for penicillin allergy. One tested positive, three had inconclusive results. [AAAAI 2021, abstract 466]

At the time of testing, the average gestational age was 27 weeks in these women. Eighty-seven women reported penicillin or amoxicillin allergy. Of these, six reported allergies from amoxicillin–clavulanate, two from ampicillin, and five from cephalosporin. In 21 women, the culprit drugs were unreported. One had a penicillin label by reason of a family history of penicillin allergy.

The index reaction occurred more than 5 years prior to testing in 90 percent of the women. Ninety-one percent of the index reactions were either cutaneous or unclassified.

All but one of the 119 women who underwent a graded challenge to penicillin V or amoxicillin tolerated the challenge. In women who passed the challenge, the penicillin label was removed, said Patel.

Of these women, 52 used intrapartum antibiotics, 38 of whom used penicillin during delivery with no adverse effects.

“People are always afraid to touch pregnant women because of the ramifications: what if they have an anaphylaxis, what if they have a reaction, what if something goes wrong …” commented Dr Jonathan Bernstein from the University of Cincinnati, in Cincinnati, Ohio, US, who was unaffiliated with the study. “But the key takeaway is penicillin testing is extremely safe, whether patients are pregnant or not.”

About 1 in 10 women believe they are allergic to penicillin. Those who have a history of penicillin allergy usually had the allergy established during childhood, but, when tested, more than 9 in 10 pregnant women who think they are allergic to penicillin are not. [JAMA 2020;323:1216]

Penicillin allergy testing could delabel the majority of pregnant women with minimal risk, paving the way for proper antibiotic application in pregnant women requiring antibiotic interventions.