One instance is pyometra, say the female had it, was treated and saved from a spay, they bred her each cycle three times and than immediate spay, another instance
performance dogs, example
schutzund trainers, will do back to back, spay than they have their whole life to do the titles they need, seeing as how breeding and cycles affect them timewise.
i have never done it, and hope i will never have to, but there are other examples i am sure due to other things such as hormones and balance of progesterone etc.....