I’ve never read it, so I can’t give a context of what’s happening here. But I have a description!
Spike’s life has always been one of boyish fantasy, lusting after the mare of his dreams and goofing off when not helping Twilight Sparkle. For as long as he can remember, he’s always been Twilight’s little brother first and assistant second. As an androgynous baby dragon, it’s always been assumed that he was male based on what other ponies, namely Twilight, have said. Why would anybody have any reason to say differently?
Following traumatic and confusing circumstances, Spike is left with an enormous question on his hands. How could he have laid eggs? Only one pony has the answer, and it will shatter the basis of his entire life. Ultimately, life is only what you make of it, and it’s up to Spike to determine where to go from there.