Taken from source:

It was a bit hard to choose which one to be pregnant with Carnation Bliss and Astral Clover but I decided to make Fluttershy to be the one since she wanted to be the trooper even though Treehugger wanted to experience it too but they both can’t go through pregnancy together that would suck dkjgndfjg 

But anyways, Treehugger spoils Fluttershy rotten throughout the pregnancy by giving her kisses, taking her to meadows to practice her breathing for labor, making delicious teas (which became Carnations passion lol), giving tummy rubs, and trying to come up with names. Fluttershy is just loving it <3