And then following pregnancies have no issues. I wouldn't be too worried about it. With nice quality litters line that I think your doing just fine!
My hystrix had 5 healthy pups and one partially developed pup delivered at night in her last litter. A couple days later she delivered 2 more dead pups, more developed than the first dead one.
So it happens, guess it's just nature, but in your case did there happen to be some sort of stress that may have caused it. Was she eating well? What # litter was it for her? Anything you can add to the circumstance that may help us figure it out, if there is anything to figure out even?
No stress that I was aware of. These rays have been together for several years. She was eating well too, and ate a good meal the night she delivered. This was her 3rd litter, I think.
I would say it's just Mother Nature. Two of the still born pups were at about the same stage of development (probably half-way developed compared to the live pups) while the third still born was much less developed. The female is 11.5 - 12" diameter so maybe 8 pups were too much for her to carry to term.