It is certainly uncommon, but not unheard of. If the dam is under stress she might kill or even eat her puppies. The lady who was performing Physical Therapy on my dad's shoulder, told me that they rescued a pregnant bitch and she ate her puppies. But then they let her be bred again and she was fine with the second litter. Personally, I do not think that it is indicative of good character. GSD bitches tend to be awesome mothers, and often foster other species. I would think that the risk that a pup out of such a situation, who did not have the experience of being in the litter with a dam, would be too high to breed her.
I do not think this really happens often enough to prove it as a heritable trait. Genetic, environmental, stress -- no matter how it comes about it does not sound like a good idea to breed her again or her offspring.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC