i have sinusitus. which drips down my nasal and throat passages. So i've coughed almost every day of my current 7 month pregnancy.
Checked with ENT and found that I have acid reflux as well (simple test - do you cough more when you lie down? Cos the bile/phelgm from the stomach comes up) .
If cough really bad, go see an ENT. Dont use over the counter medicines and dont use medicines which were prescribed for other mothers since they may have other symptoms and conditions which are not the same as yours.