the standard pet policiesThese cover absolutely nothing to do with or any problems connected from breeding, pre, during or even weeks after, so no good whatsoever if a bitch were to have any sort of problem.
Breeders insurances are expensive and as already said you need to be covered at least 6 months before. Make sure that you read them through though to see what they cover. I always used to use them, and then one year I decided they were a waste of money and opted out to end up with a £1,000 vets bill.

So I would recommend having one, just in case, or as Setters4me has suggested put some savings away or have a credit card ready for use just in case. ;-)