Your skin is more sensitive because of all the extra blood and pressure in your vessels down there. It'll hurt more than if you weren't pregnant, but as long as you know what to expect, there's nothing wrong with getting waxed. If this is your first wax ever, I wouldn't recommend this as the time to do it. You might try a depilatory cream like Nair instead. Don't use a razor. Nicks and cuts could lead to infection and it's hard enough to reach down there.