Hi Forgetful, firstly, did she have these pups in march or are you from the USA[and reverse the date] and they are only a few days old?
If they were born in March and we are talking about a six month old pup....then yes this is pretty unusual, surely the pup would have been big enough to get out of her way!!
If they were only born a few days ago then it's a different story. Bitches will sometimes, especially with a large litter accidently suffocate a puppy, it's hard her her to keep track of where they all are! A bitch may also intentionally euthanise a puppy, they seem to have an inbuilt sense of something being wrong with a pup, and will either take this route or push the pup away and refuse to feed it.....they do know whats best. Although that said, I have raised pups that my bitches have 'pushed' away, but it takes a lot of hard work[but very rewarding].
Please let us know which one of these applies and we may be able to offer more advice.
Lisa x