i am confused

dear sir, regarding mcqs asking whish drugs are contraindicated in pregnancy and lactation.

i read - no drug is absolutely contraindicated in lactation.

but how about lithium, tetracyclines,nalidixic acid ,sulphonamides?

then are lithium and warfarin absolute or relative contraindications in pregnancy?

we do give warfarin from 12 -37 wks in women with prosthetic valves.

please help.