Cohort Study of Pregnancy Outcomes After Exposure to Fexofenadine or Olopatadine in the First Trimester.

Medication safety must be carefully considered during pregnancy because of the potential risks to the fetus. Allergic diseases during pregnancy, oral second-generation antihistamines, such as fexofenadine and olopatadine, are often used when topical agents are insufficiently effective. However, there are limited data on their teratogenic risk, particularly in the Japanese population. A cohort study was conducted using data from Japanese teratogenicity information services at two institutions: Toranomon Hospital and the National Center for Child Health and Development. Outcomes in pregnant women exposed to fexofenadine or olopatadine during the first trimester were compared with those in controls exposed to nonteratogenic drugs. The primary endpoint was the incidence of major birth defects defined by the EUROCAT criteria. Secondary outcomes included preterm birth and low birth weight. Logistic regression analyses were performed with adjustment for maternal age, alcohol consumption, smoking, and comorbidities. In total, 1473 eligible pregnancies for the analysis of major birth defects were included. Major birth defects occurred in 1.8% of the fexofenadine group (n = 231) and 3.0% of the olopatadine group (n = 186), showing no significant increase compared with 1.8% of the control group (n = 1056). Logistic regression showed no association between either antihistamine and major birth defects, preterm birth, or low birth weight after adjustment. No consistent pattern of anomalies was identified. This study found no evidence that exposure to fexofenadine or olopatadine in the first trimester increases the risk of major birth defects. These second-generation antihistamines appear to be relatively safe in pregnant women with allergic conditions.