
Pregnancy and birth have always been risky. It isn't until advanced medical practice, frequent ceasareans and excellent monitoring of pregnanct women, not to mention better general health that fewer women die in childbirth or shortly after. It used to be the most common reason for death in women of child bearing age!
Unfortunately a lot of the same things and more can go wrong with a canine pregnancy. Bearing in mind that many breeders have little midwifery expereince, are unlikely to be able to monitor things in the way a human birth would be.
Often it is difficult to tell the diffference between normal and a problem before it is too late, bitches and puppies sadly do die.
I know of three bitches in my normally easy to whelp natural breed diue in pregnancy/during birth and in all three cases all were lost. Two were expecting their first litters and were Champions, and the third had already had a litter without problems.