i'ver allergic asthma , during the attack i only take anti-histaminic and mucolytic are they safe during pregnancy?

The perfect method to treat asthma is to avoid having an attack in the first place. Avoid exposure to your asthma triggers.

Don't smoke. A pregnant woman who smokes runs a highly increased risk of having a severe asthma episode at some time in the pregnancy.

Stay away from people who have a cold, the flu, or other infection.

Long-term control medicines are consumed daily to control asthma and prevent asthma symptoms, even when asthma is stable. Theophylline is a long-term control medicine, slackens the smooth muscles around the airways.

Using a spacer with inhaled steroids (metered-dose inhaler) and gargling your mouth after inhaling the medicine minimises the risk of thrush.

Mucolytic agents maximises bronchospasm, and antihistamines are not useful in the treatment of asthma.

Health-disease.org

BUT We always advise to talk with your health care provider befor taking any medication.
Antihistamines (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

American Academy Of Allergy Asthma & Immunology