Have any breeders noticed certain problems recurring recently?
Such as - smaller than usual litter in numbers, under-sized puppies, dead/mummified puppies, deformed puppies (ie hole in stomach and chest area)?

Any thoughts on possible causes?

I recently had a lab litter like this (just 4 puppies, 1 healthy) and we have established it is not genetic. I have also established that these problems have been experienced in the UK and USA (havent heard of any in Australia or New Zealand yet).

My vet and I would love to get to the bottom of this and are trying to collect as much info as possible. All replies welcome.

I have'nt experienced this myself but know quite a few breeders in the uk which are having the same sort of problems.
Where abouts are you in the world?

Kind of makes you wonder if the food we are feeding our fur kids might be some of the problem...

I live in the UK and feed my dogs on a raw-food or species appropriate diet. (no commercial food at all) I breed dogs and have found similar problems locally. My problems I think stem from the drugs my vet pumped into them, not the food they are fed. Seriously considering trying to find a holistic/homeopathic vet (good luck huh!)

Hope that helps