Most antihistamines sold to the public do carry a warning that they should be avoided in pregnancy, and this applies to Telfast. However, there is no evidence that non-sedating antihistamines such as Telfast are harmful to the foetus in any way. The caution about them is due to the fact that there is currently insufficient evidence to prove that these drugs are totally safe. Most experts agree that non-sedating antihistamines may be used during pregnancy if they are required for control of allergy symptoms.