We've had 3 dogs recently lose pups in utero the week before they were due to whelp. We were able to save one female, but lost the other 2. Have you heard of anything like this?

I have a question and was hoping you could help me. We switched to the raw diet last year and have been purchasing books from you and giving to our puppy customers and refer to your web site from our web site. I have just had 3 dogs in a row the week before they were due to whelp have puppies die in utero (hindsite now), the mom bloated real big (she was full of amniotic fluid), went into labor early....The first lost the litter but we saved her. The second two died suddenly. It seems they were toxic from the dead puppies. I have never had any problems with any of my dogs breeding and now just had this 123 punch. We are all devastated over the loss of our 2 mama dogs. Have you ever heard of anything like this? I'm getting all paranoid that it is my fault for not knowing the signs and just thinking they were getting fatter from puppies when it was fluid. I'm blaming the raw diet but know that isn't realistic. Or if I'm feeding too much or not enough organ or supplements? Did my luck just run out and problems of course are bound to happen? When death happens it makes me feel like how can I keep doing this......but of course I see my happy healthy puppies and all the families we share that with. It is just very difficult to deal with this loss. Every time I ask a vet they just don't know anything when it comes to breeding. We really appreciate you taking the time to read this and answer.