Without any interference during their first heat, they'll simply grow into mostly realistic proportions (though their genitals are much larger than is realistic). The growth gained from sex is more magical than natural, and won't pass on to offspring. Though, it can get pretty crazy when a chain of mares fuck others as they go into heat. The growth from sex is usually more intense than the previous mare, so when Sweetie Belle decides to go down on one of her friends, they'll be bigger than her, and so on and so forth.

Since their rather productive day at the spa, the spell changed Fluttershy greatly, her cock having grown to two feet, and her balls bigger than canteloups in the last few weeks. And she'd grown very messy, a stream of cum blasting out of her cock at all times. Condoms no longer worked for her, and so a mess was made everywhere she went. Thankfully, her cottage was build with drainage into a massive storage vault nearby. She'd borrowed several spells rune from Twilight, including one that would let her temporarily grow a second cock, and was eager to try them out.

Fluttershy was currently out in a field, pleasuring herself. She'd used the run to grow a second dick, just as long as her first. Sitting on her ass, she grabbed one of her breasts, and positions a cock in front of her nipple, pressing the tip onto it. Holding it in place, she reaches down and presses on another run, her nipple suddenly engulfing her cock. She then does the same with the other, both cocks stuffed inside her breasts.

Author's Note

This chapter is unfinished. I've left this fic, and many others, for so long that things have changed, and I no longer remember what i originally had planned... but do not despair, for I'm planning on doing a huge rewrite, mixing concepts from many of my fics into one!

The previous chapters, which I'd hidden for rewriting, are shown again, and may not make full sense anymore, but rather then keeping them gone and hidden, im just letting you all have them once more