
My thoughts about this have been well documented here! Fact is I'd only scan if I needed to make a decision about a gravid spay, or not. And as that's unlikely to have ever been needed, frankly I don't bother with scanning, which after all isn't accurate re numbers, and at best, only confirms a pregnancy at the time of the scan. Not guarantee the bitch will carry to term. I realise, only too well, that others disagree, but that's my two-bits worth!!
By the time your bitch gets to 7 weeks, you should start to see the puppies moving around, unless she only has a couple and has them tucked up under the ribcage.
For me, I'd wait until a couple of days after her due date and if nothing has happened, get her checked by your vet, palpated, perhaps x-rayed /given a shot to get things moving. Provided you had perhaps a couple of good matings, why not wait?
ps Vet offices are where sick dogs go (infection). Many dogs hate going to a vet (stress). Others will disagree, and have, but when I plan a litter, I curtail all my other dog-related activities, showing etc.