Hi, I have heartburn, too. But I'm not on zantac. I alternate between rennies & tums. It might be just in my mind, but it seems like my body develops a "resistance" to them if I don't swap brands occasionally. I wake up most nights with bad heartburn at around 2am and that's although I usually take two tablets before going to sleep. It's quite annoying, but to be honest, for me it's the only bad pregnancy symptom, so I feel very lucky.