The following information is taken from a reliable source of prescription drug information, Lexi-Comp.
For Singulair the statement below, is not the equivalent of a statement that the drug has been shown to be safe.
For Zyrtec the statement suggests that this drug is probably safe but that there is not enough evidence to confirm that belief.
You may want to discuss this information with your doctor.
The most conservative approach would be for you to avoid these drugs unless they are deemed necessary by you and your doctor.
Good luck
Pregnancy Considerations
Montelukast (Singulair) was not teratogenic in animal studies, however, there are no adequate and well-controlled studies in pregnant women. Based on limited data, structural defects have been reported in neonates exposed to montelukast in utero; however, a specific pattern and relationship to montelukast has not been established. Healthcare providers should report any prenatal exposures to the montelukast pregnancy registry at (800) 986-8999.
Pregnancy Considerations
Maternal use of cetirizine (Zyrtec) has not been associated with an increased risk of major malformations. The use of antihistamines for the treatment of rhinitis during pregnancy is generally considered to be safe at recommended doses. Although safety data is limited, cetirizine may be a preferred second generation antihistamine for the treatment of rhinitis during pregnancy.
my doctor said that clairitin and zyrtec are ok, but not allegra.