Antihistamines are frequently needed by pregnant women for the treatment of allergic disorders. Most second generation antihistamines carry a Pregnancy B rating but, for example, Allegra (fexofenadine) is Category C (Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks).
The achievement of a Category B rating indicates that adequate studies in pregnant women have demonstrated that treatment does not increase the risk of congenital malformations to the fetus during the first trimester of pregnancy and in later trimesters.
Most intranasal steroids have a Pregnancy C rating.
The 2001 ARIA guidelines conclude that the older antihistamines have an overall unfavorable risk/benefit ratio, even in the nonpregnant population, because of their poor selectivity and their sedative and anticholinergic effects, and therefore, where possible, first-generation antihistamines should no longer be prescribed as AR therapy.
In a 2000 joint position statement, the American College of Obstetricians and Gynecologists and the ACAAI recommended consideration of cetirizine and loratadine, preferably after the first trimester, for pregnant women who cannot tolerate chlorpheniramine or tripelennamine.
The current recommendation is to first consider chlorpheniramine, tripelennamine, or hydroxyzine if an antihistamine is needed during pregnancy.
In a study of 210 pregnancies in which loratidine had been taken vs 267 pregnancies in which other AH (both 1st and 2nd generations) had been used and most of the exposures was in the first trimester of pregnancy, there was no significant difference in the incidence of congenital abnormalities in children born to women who had taken loratidine (2.3%), other AH (4%), and no AH (3%) during pregnancy. However, the incidence of miscarriage was higher in those pregnancies in which loratidine had been used. In other studies, Benadryl has been shown to have oxytocin-like effects, especially in high dosages.
Physicians must decide on a case-by-case basis whether to select one of the older, better-studied antihistamines, thought to be safe during pregnancy, or a newer agent that has less adverse impact on quality of life but is less well studied in pregnancy. According to a Medscape review, the dilemma can often be averted by prescribing an intranasal steroid instead of an oral antihistamine. This statement however is controversial, considering that most intranasal steroids have a category C rating in pregancy.
Most oral and inhaled steroids are also Category C. According to one meta-analysis, although prednisone does not represent a major teratogenic risk in humans at therapeutic doses, it does increase by an order of 3.4-fold the risk of cleft palate and cleft lip, which is consistent with the existing animal studies. Of the inhaled corticosteroids, budesonide is currently the only one that is category B.
C category during pregnancy
B category during pregnancy
Update from 2015: The “Pregnancy and Lactation Labeling Rule” (PLLR) requires changes to the content and format for information presented in prescription drug labeling. The PLLR removes pregnancy letter categories – A, B, C, D and X.
Antihistamine use during pregnancy. AAAAI.
Safety of AR Drug Classes During Pregnancy Antihistamines. Medscape.
Over-the-Counter Medications in Pregnancy. AFP.
Treating Asthma and Comorbid Allergic Rhinitis in Pregnancy: A Review of the Current Guidelines. Barbara Yawn, MD, MSc, FAAFP; Mary Knudtson, DNSc, NP
Birth defects after maternal exposure to corticosteroids: Prospective cohort study and meta-analysis of epidemiological studies. Teratology, Volume 62 Issue 6, Pages 385 - 392.
Patient response to different antihistamines will vary http://goo.gl/Q2PiV
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