Allergen-Specific Immunotherapy During Pregnancy Appears Safe for Babies

By Scott Baltic

May 20, 2022

NEW YORK (Reuters Health) - Maintaining allergen-specific immunotherapy (AIT) during pregnancy shows no evidence of raising the risk of congenital malformations or other adverse pregnancy outcomes, according to a nationwide study from Sweden.

Although a few earlier studies evaluating AIT in pregnant women have come to similar conclusions, they were small "and guidelines continue to recommend against initiating AIT during pregnancy," researchers note in the Journal of Allergy and Clinical Immunology: In Practice.

To learn more, Dr. Niki Mitselou of Orebro University Hospital and her colleagues extracted data from Swedish national health registries on more than 900,000 singleton live-birth pregnancies between 2005 and 2014.

Sublingual immunotherapy to treat grass pollen seasonal allergy was introduced in Sweden in 2005. Dr. Mitselou noted that starting AIT during pregnancy would have been discouraged during the study period, while maintaining well-tolerated AIT would have been be encouraged.

The decision to treat women of child-bearing age with AIT would have depended on whether "the patient herself had plans of getting pregnant soon, with the risk that this coincides with the AIT induction phase," Dr. Mitselou told Reuters Health.

Of the overall cohort, 743 pregnant women had a record of exposure to AIT three months before conception until gestational week 22.

The rate of congenital malformations in those women was not significantly higher than that in other women in the cohort (4.4% vs. 3.9%, respectively; adjusted odds ratio, 0.90; 95% CI, 0.63 to 1.27). Nor was AIT significantly associated with other adverse pregnancy outcomes, such as preterm birth, stillbirth, or cesarean delivery.

Dr. Anne Ellis, professor and chair of the Division of Allergy & Immunology at Queen's University, in Kingston, Canada, told Reuters Health that both the American Academy of Allergy, Asthma & Immunology and the Canadian Society of Allergy and Clinical Immunology "recommend continuing maintenance immunotherapy during pregnancy but not to initiate or do any dose escalation during pregnancy."

This is primarily because of "the small but measurable risk of anaphylaxis during build-up, which obviously we would like to avoid in a pregnant patient," she explained.

Dr. Ellis, was not involved in the study, added that while it has been known that continuing subcutaneous AIT maintenance dosing during pregnancy is safe, "more data supporting this commonly held opinion is always reassuring and helpful."

SOURCE: The Journal of Allergy and Clinical Immunology: In Practice, online April 26, 2022.