Pregnancy Outcome Following First-Trimester Exposure to Bilastine: A Comparative Observational Cohort Study from the...

Background: Bilastine is a long-acting, nonsedating antihistamine used to treat allergic conditions. Human pregnancy experience with bilastine remains limited. Objectives: The primary aim was to evaluate the risk of major anomalies following first-trimester bilastine exposure. Secondary endpoints included additional pregnancy outcomes. Methods: This observational, prospective cohort study included women counseled by the Israeli Teratology Information Service regarding first-trimester bilastine exposure between July 2019 and June 2023. Participants were contacted by telephone for follow-up using a structured questionnaire. Pregnancy outcomes were compared with fexofenadine-exposed pregnancies. The data analysis, comparison, and presentation followed the recommendations of the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guide. Results: Follow-up was obtained for 36 pregnancies with at least first-trimester bilastine exposure. The median daily bilastine dose was 20 mg, with treatment discontinued at a median gestational age of 5 + 6 weeks. First-trimester bilastine exposure was not associated with an increased risk of major anomalies [bilastine: 2/33, 6.1% vs. fexofenadine: 2/27, 7.4%; crude OR 0.81, 95% CI 0.11-6.14]. No pattern of malformations was observed. Rates of live-birth, miscarriage, and pregnancy termination were 91.7%, 5.6%, and 2.8% in the bilastine group, and 72.2%, 19.4%, and 8.3% in the fexofenadine group, respectively. Conclusions: This cohort study, although small, provides preliminary reassurance for counseling regarding inadvertent early pregnancy exposure to bilastine. Larger studies are needed to validate these findings.