Agents used to treat the common cold and its symptoms, their efficacy and their safety in pregnancy, continued

Chlorpheniramine and diphenhydramine have mostly reassuring pregnancy data and should be considered the preferred antihistamines in pregnancy.

Most of the older antihistamines are not considered to increase the incidence of congenital malformations in humans. Although some antihistamines have been associated with oral clefts in retrospective studies, others have found no significant increase in the incidence of major or minor malformations, and one study even found that significantly fewer infants with malformations were exposed to antihistamines while in utero than were controls.

There is accumulating reassuring human data on the use of newer antihistamines fexofenadine, cetirizine, loratadine, and clemastine in pregnancy.

Animal data for codeine, dextromethorphan, and hydrocodone are conflicting.

Human data for all of these agents are poor. Guaifenesin was associated with inguinal hernias in one study only. A large case-control study observed an association between first-trimester use of opioids and various congenital anomalies.

Neonatal withdrawal has been reported in babies born both to addicted and non-addicted women who took codeine in the days prior to delivery. Codeine ingestion near the time of labor can produce respiratory depression in the newborn.