Two of the greatest enigmas of Equestria had always been:
(1) Why is it that only a single colt is born per every fifteen fillies?
(2) Why is it that of these fifteen fillies, seven will be barren?
The discovery of chromosomes, and genetic testing, solves once and for all these enigmas, but at the personal cost of every mare who had yet to be pregnant.
Would she voluntarily test, or would she just try and try, each time praying that she wasn’t among the 43.8% of apparent mares among the Equestrian population?

(Don't ask me about the luck of this or that mare on the show. Other that the first chapter, I tried to be fair and rolled dices for the Mane 6, their relatives and a few others. And even 'good news' may not be so good.)

(I'm not sure how often I'll be updating this story. I have already seven half-written chapters, but I need to be depressed to push them out.)