With so much debate around the ethics of diamond mining, you wouldn't be the first bride to decide not to add to the demand. Conflict diamonds now make up a much smaller percentage of the world's diamond production than they have previously, but if you want to be sure your gems didn't come from a conflict zone, your best bet is to look for an antique ring. You might even decide to forego diamonds completely and opt for a coloured gemstone instead.
Top tip: the four Cs still ring true for vintage diamond rings: cut, clarity, colour, and carat. Your jeweller should be able to tell you about these.