Don't you think a bitch that has difficulty free whelping could pass on the same problem to her bitch puppies? Something to think about, I'm not telling you what to do. You asked for thoughts.
I do think that is possible. I have been told that if your bitch has trouble whelping, then her offspring may have some of the same problems. After taking it all into consideration. I agree with both sides of the issue. In this case however, I feel that its best that I retire her. She's been a great dog, and she has earned her retirement.