I had the pharmacist show me on their chart. Zantac 75 2x a day is safe. But if you get it every time you eat, you should talk to your doctor about the possibility of gallstones which is common in pregnancy.
Talk to your doctor...they actually have me on prilosec and it's amazing for the acid/heartburn (prilosec is a class C drug, zantac is a little safer as a class B, but didn't work for me) but unfortunately I still wake up chocking on stomach content if I eat or drink after 5pm (it just doesn't burn like before)...it's stupid pregnancy hormones that are keeping the valve that is supposed to keep your stomach content in your stomach from working correctly
I agree to ask your doctor first. I did and for me he said that it was fine, but everyone and every pregnancy is different :-)