Pregnancy outcome after gestational exposure to loratadine or antihistamines: A prospective controlled cohort study

Background: Loratadine is a second-generation histamine H₁-receptor antagonist, used in the treatment of allergic conditions. No prospective controlled trials on loratadine in human pregnancy have been published to date. Objective: To determine whether the use of loratadine or other antihistamines (OAH) is associated with an increased risk of major anomalies. Methods: Callers who were counseled by the Israeli Teratogen Information Service in regard to loratadine or OAH exposure during pregnancy were prospectively collected and followed up. Pregnancy outcome was compared among three exposure groups: loratadine, OAH, and a control group of patients who were counseled for nonteratogenic exposure, nonteratogenic controls (NTC). The OAH included astemizole, chlorpheniramine, terfenadine, hydroxyzine, promethazine, and dimetindene. Results: We followed up 210 pregnancies exposed to loratadine (77.9% in the first trimester) and 267 pregnancies exposed to OAH (64.6% in the first trimester) and compared pregnancy outcome with that of 929 NTC. The rate of congenital anomalies did not differ among the groups [loratadine: 4/175 (2.3%), OAH: 10/247 (4.0%), NTC: 25/844 (3.0%), P = .553, relative risk (RR), 0.77; 95% confidence interval (CI), 0.27 to 2.19, (loratadine vs NTC); RR, 0.56; 95% CI, 0.18 to 1.77, (loratadine vs OAH)]. The rate did not differ between those exposed to antihistamines in the first trimester and the control patients [loratadine: 1/126 (0.8%), OAH: 7/146 (4.8%), NTC: 25/844 (3.0%), P = .152, RR, 0.27; 95% CI, 0.04 to 1.94, (loratadine vs NTC); RR, 0.17; 95% CI, 0.02 to 1.33, (loratadine vs OAH)]. Conclusions: This study on the use of loratadine in human pregnancy suggests that this agent does not represent a major teratogenic risk. The study was powered to find a 3-fold increase in the overall rate of major anomalies.