
I have written about my feelings re scanning before

But to repeat - scanning only confirms, or not, a pregnancy at the time of the scan. It's rarely totally accurate either. And unless you have somebody come to do the scanning at home, why risk stress/infection by taking a pregnant mum to the vet when she should be calm and taking it easy throughout. I have been told that people need to know so they can plan ahead (I didn't need to do this - we just planned the mating and cleared our appointments for the time it would all take). If you need to know about puppy-size (unplanned mating) it's far better to do an x-ray a few days before the due date to see whether she'll need a C.Section or not.
Today's breeders seem to think scanning is something that has to be done. I'm old school and don't.
Just to add, even if a scan says no, wouldn't you still be watching as her due date approached - I know I would!! And I'd rather put the cost of the scan towards things like a potential C.Section, other vet bills, food, registration and so on.