I can't imagine there's anything you can do for polyps. Unlike my chronically irritated GB, which could be less irritated if I kept to a low-fat, bland diet (although that didn't work forever), there's nothing you can do to get rid of polyps or make them less obtrusive. Unless there's a chance they will go away on their own, I don't see why your doctor wants you to be miserable for an entire year (might be a good question to bluntly ask him).
There is something about pregnancy that messes up gall bladders. It's one of the reasons why women are more likely to have a bad GB than a man. (Weight, age, fair skin, genes, and certain heritages, like Native American, also make one more prone.)
I was 18 when mine went bad, but I had a family history. My mother's side of the family have had a lot of bad GBs, and my father's mother thinks hers is bad, but thankfully it only has fits every once in a while, so she's managed to live with it.