when it comes to any medication -- over the counter or prescription -- you need to call your obstetrician's office for patient-specific advice and recommendations. i can assure you that they have had this question before. while many ob's have prescribed codeine-containing cough suppressants others will not use them. honey is a good cough suppressant too. and considered safe if store-bought and purified. the real question might be the underlying reason for your cough. that maybe something you should investigate before treating it.
are there any over the counter cough meds that are safe in the 3rd trimester to use?