
I did take a bitch to be checked last year. First time I've done this. I have a very small toy breed, well known for difficult whelpings. I have been working on a self whelping line for what seems like a million years.
I had had a judge round to look some pups over, and he told me that this girl was the one I should keep. This particular bitch was smaller than the bitches I had bred from previously. But I had bred her myself, and she was from a line of self whelpers. I told the vet that I wanted her checked over when she had her booster jab. He was totally happy with the width of her pelvis and told me that he had no worries.
I was still apprehensive, mostly because she was smaller than I would usually use. So, a month later when she came into season, I went back to ask if he was sure!!! Poor girl was re-checked, and he insisted that he saw no reason why I shouldn't mate her. I realise that he can't foresee inertia, but I would recognise that anyway.
She whelped with no problems. :-) So, in answer to your question, experienced breeders
may feel the need to see the vet early on. I guess it depends on circumstances. My vet is very familiar with my dogs, and we have a good relationship. I may not have had a bitch checked by a vet I didn't have the same rapport with. So I reckon you will get differing replies.