A good rule of thumb is anything you wouldn't ordinarily lift. I'm not lifting tins of paint or owt, just in case! Though when I worried myself earlier on (I carried a big tin of paint from town home) I got stretchy pains which obv freaked me out a bit, I posted on here and everyone said not to worry etc, and they were right. But if you're a worrier, try not to lift anything that makes your innards pull!