What its class a or class b medication for pregnet woman? what safe to take ?

A = safest: Category a: these drugs have been tested and found to be safe during pregnancy. Category a includes drugs such as folic acid, vitamin b6, and some thyroid medicines in prescribed doses. Category b: animals studies say safe, but no randomized controlled studies done in humans. These drugs are frequently used during pregnancy and do not appear to cause major birth defects or other problems.