Some things you can do to help prevent it is to cut back on sugars (thrush feeds on it - when you are pregnant, there is more glucose than normal so they basically have a feast!), eat yoghurt or drink yakult or even better, take acidophilus capsules. I have been taking 'Inner Health' lately and whenever I feel a case of thrush coming on, it usually stops it so fast. You'll need to ask your pharmacist for it, it's stored in the fridge as it is a live bacteria (a good one!) and is safe in pregnancy.