Review shows gaps in research on anaphylaxis during pregnancy

Researchers called for more studies into the risks for anaphylaxis during pregnancy, citing scarce research on the subject, according to a systematic review published by The Journal of Allergy and Clinical Immunology: In Practice.

Anaphylaxis occurs in about 1.5 to 3.8 of every 100,000 pregnancies, according to Sophie Carra, MD, of the department of allergy at University Hospital of Montpellier in Montpellier, France, and colleagues.

However, the researchers said, a search of the MEDLINE, Cochrane, Lilacs, Scielo and Science Direct databases only yielded 12 qualifying articles related to the term “anaphylaxis during pregnancy.”

When anaphylaxis does occur, the researchers continued, it might not be diagnosed. Pregnant women tend to have lower blood pressure, for example, and cutaneous signs could be missing in approximately 35% of cases.

Clear definitions and guidelines would aid identification of anaphylactic reactions during pregnancy and prevent risks to both mother and child, the researchers said. But only seven of the 12 articles focused on diagnosis and management of anaphylaxis during pregnancy.

Also, only two of the articles defined anaphylaxis, whereas three used the Ring and Messmer degree of severity. The rest of the articles only described the clinical manifestations of anaphylaxis.

Only one article reported on maternal mortality rates, which varied from 0% to 5% with an estimate of 0.005 per 100,000 live births, and all five deaths described occurred during caesarean sections, mainly due to neuromuscular-blocking agents.

Additionally, only 25% of the articles mentioned the negative impact on newborns, including encephalopathies, transfer to the NICU and preterm births, and very few articles described data related to the postpartum period.

The main causes of anaphylaxis overall included beta-lactam antibiotics (58%), latex (25%) and anesthetic agents (17%). However, the researchers noted that only 17% of the studies described how allergy testing identified the causative agents in anaphylactic cases.

Cesarean delivery was included as a specific cofactor for anaphylaxis in one study, along with a clinical history of allergic reactions and being Black.

Of the articles that proposed a management strategy, most proposed the same management and treatment for a clinical episode of anaphylaxis during pregnancy that are recommended for nonpregnant patients.

The seven articles that offered management guidelines recommended the use of epinephrine, but without any details about the dose or the patient’s position, and none of the articles provided details about serum tryptase.

The researchers said they were surprised by the small number of studies related to anaphylaxis during pregnancy, considering the risks it presents to both mother and child. They also noted the lack of collaboration between specialists such as allergists, anesthesiologists, and gynecologists and obstetricians in writing these studies.

To improve recognition of anaphylaxis during pregnancy, the researchers urged allergy academies to propose clear, standardized definitions. The researchers also recommend international classifications to increase the accuracy of anaphylaxis data.

When anaphylaxis does occur and the acute phase has been treated, the researchers recommended referral to allergists for etiological confirmation, risk stratification, and specific guidance on the need for epinephrine auto-injectors or information about possible cross-reactivity between allergens.

Considering the risks presented by antibiotics, anesthetics and latex, the researchers recommended allergy workups early in each pregnancy, as well as routine surveillance during prenatal visits with specific questions about reactions to latex and casual contacts.

This review was limited by its small sample of articles and its narrow geographic range, with data possibly reflective only of wealthy countries. The evolving nature of treatment and definitions also was a challenge, the researchers said.

However, the researchers emphasized the critical nature of the gaps they found in research, which they said should be considered in future public health strategies.

“A national or multinational registry of anaphylaxis in pregnancy would begin to answer many questions despite some of the inherent reporting biases,” the researchers wrote. “Also, a collaboration between different specialists involved in the care of pregnant women should be established in order to support preventive strategies and reduce avoidable deaths due to anaphylaxis during pregnancy.”