I suffered from acid reflux before i got pregnant and got horrific heartburn in my first trimester and found myself going through a 500ml bottle of Gaviscon a week, but it blissfully went away during my second. And then it returned for the third with vengeance, so much so that i was waking at night with mouthfuls of stomach acid! YUCK!
One of the things i was given before i was pregnant was a proton pump inhibitor (PPI) which suppresses acid production, thus reducing heartburn and acid reflux. When it returned in my third, i was so miserable with it, i started researching via google whether i could take some of the PPI's i had leftover.
The upshot was, i found 1 particular one, Omeprazole, that has had limited testing in pregnancy but from what testing has been done seems to be safe during pregnancy. I spoke to my GP who said that provided that i was aware that it wasn't fully tested and i was well into my third trimester that he was happy for me to try it and see how i got on. He gave me the lowest dosage available and said 1 to 2 per day but i've just been taking 1 every other day or so, as i don't want to put my little one at more risk than necessary, but the dosage i've been taken is working a treat. I'm not heartburn free, but that's purely because i frequently forget to take it as i'm heartburn free at the time I'm supposed to remember!
Its actually the best PPI i've ever taken, and i usually find that heartburn starts to disappear within a few hours of taking a capsule so it seems to be pretty fast working too. I realise that as its not fully tested a lot of people wouldn't want to even try, but i was at my wits end and decided, for us anyway, that the benefit outweighed the risks. My mum had an equivalent when she was pregnant with me and my brothers and none of us have any problems other than inherited heartburn! If you get really desperate, it may be worth doing some research into it yourself and maybe having a chat with your GP if you decide you'd like to try it, some will let you (like mine, who is great) but others won't.
I honestly can't recommend it enough, but i do understand a lot of people would be hesitant or refuse outright