8/19/03 Antihistamine use during pregnancySummaryAntihistamines (AH) are frequently needed by pregnant women for the treatment of allergic disorders. However, there are concerns in pregnant women raised about possible teratogenic effects of AH (as true for many other medications). There is much less known about the safety of the second generation AH such as loratadine (Lor) in pregnancy than the safety of the older (first generation) AH such as chlorpheniramine in which there is much more experience. However, there is more potential for other adverse effects such as sedation with such first generation AH. Therefore, Diav-Citrin et al of the Hadassah Medical School in Jerusalem, Israel followed 210 pregnancies in which Lor had been taken vs 267 pregnancies in which other AH (both 1st and 2nd generations) had been used. Comparisons were made with a control group (no AH during pregnancies). Most of the exposures occurred during the first trimester of pregnancy. They found no significant difference in the incidence of congenital abnormalities in children born to women who had taken Lor (2.3%), other AH (4%), and no AH (3%) during pregnancy. However, the incidence of miscarriage was higher in those pregnancies in which Lor had been used. Reference J Allergy Clin Immunol 2003;111:1239-43 Editor’s Comments It has been unfortunate that medico-legal and other concerns have limited the study of the safety of second generation, non-sedating AH in pregnant women. This lack of information is especially frustrating since it is increasingly recognized that the sedative and other cognitive effects of the first generation AH can have major adverse effects on driving and other functions. Dr. Michael Schatz, a leading investigator of the treatment of allergies and asthma in pregnancy, has pointed out that animal studies have suggested that Lor and cetirizine, another second generation AH are likely non-teratogenic when used in usual doses (reference: Clin Allergy Immunol 2002;17:421-6). However, there is even less information about the safety of other second generation AH. The results described above are reassuring to a degree although the population sample studied is relatively small. This study is probably not of sufficient statistical power to detect a small but significant increased risk of abnormalities such as hypospadias in those treated with AH.
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