I have a question regarding removing rear dewclaws.
When I purchased my now 4 year old dog she had no front dewclaws but her rear dewclaws were still there.  I asked the breeder about this and I was told that he has lost a pup in the past from removing certain types of dewclaws and now he allows his vet to decide if it is safe to remove the dewclaws dependent on how or if they are attached to the bone. 
So four years have gone by and I have had 0 problem with her dewclaws other than making sure I keep them clipped and she is in the field constantly so all is fine with that.
The thing is she is now due to whelp a litter of pups in the next few days and I feel there is a good chance I will end up with a pup or two with rear dewclaws.  I feel that I should have them removed since that will be expected for hunting/field trial dogs however the conversation I had with my bitches breeder keeps popping into my head. 
So I was wondering if anyone on here can give me some input on when it is not safe to remove dewclaws?  I obviously do not want to risk loosing a puppy to remove dewclaws but many feel they should be removed no matter what and I am not sure if that is truly the case.

Rear ones are and can be a problem and i would remove them. Needs to be done within the first few days. Someone that knows what they are doing whether thats another breeder or a vet, not a novice

What breed? I think it depends on the breed and how the dewclaws 'sit'. I had a dog with rear dews (very flexible, not rigid) and never had a days bother with them.

Well fwiw, I'd certainly have any rear ones removed - and by a vet!   When in Canada, my then vet didn't like doing them and in truth, we indeed lost one, we assumed, because he maybe wasn't as strong as the others (neither of us noticed any difference with him) and having this very minor procedure done (at days old) pushed him over the edge.   After that, we didn't have them taken off - this was with Bassets and at the time, in the UK, the front dews were always taken off - many breeders feeling it 'made for a neater-looking foot'.   This changed, mainly because overseas, they were not normally removed and many UK Bassets were being exported at the time.  We didn't get back dewclaws appearing.

My Whippet had her's removed but my current Basset still has his.  

I had a friend who'd do this herself and I 'helped' at one point - never again.   I didn't like it one jot even if they were days old. 

So your breeder had a similar situation to me although I don't understand 'what type of dewclaw'.   To be done correctly, from what I remember with mine/my friends, the little bone attachment needs to be removed.

Some breed standards actually specify that there should be rear dew claws

I would also want to know what breed...

I wouldn't make the choice based on trying to please puppy buyers and what you think they want:  Make the choice based on your own preferences and what you think is best, health-wise and ethically, for the litter.  Not on trying to please hypothetical others.

I always remove rear ones but never front. And I get actual extra full toes. Once I had a pup who had two extra toes on each hind paw. It was the smallest pup in the litter (large litter) who had to be topped up with bottles. I removed the four extra toes myself -not something I enjoyed but the day fell on a weekend so the vet wasn't open. It was a large wound but young pups heal easily. This dog is now 2 years old and earlier this year when I met him and his owner I had a look at his feet and they looked normal. Asked his owner if she had ever noticed anything unusual, she said no.

I've never had a problem other than that the vets seem to leave too much bone behind so you can feel and see where the claw would have been. I also have a toybreed and get the exact same with them, again never had a problem.

> the vets seem to leave too much bone behind

Yes, that needs to come off or there's a noticable knot.

Thank you so much for all the input it has helped quite a bit. 
I think that I will just go ahead and have a vet take off all the dewclaws.

That is providing you’ll find such a vet :) Many are refusing to do it these days. It is legal, but they cite that Royal-Vet-something organisation (which oversees all vets conduct ethics etc) is against it and so they are following their advice.

Edit sorry just seen you are from the States.  Much easier there :))