Artist’s own desc:
It had been a while since their little herd went out on a date; they were usually too busy. They had plenty of time now however, considering 3 of them were each due fairly soon.
Applejack, Fluttershy, and Pinkie Pie had clung to their jobs as long as they could. Applejack in particular had to be dragged away from her apple trees, grumbling the whole time about how she was fine- “it ain’t like I’m dead.”
“No, but you’re bigger than a beach ball, and you should keep all 4 of your hooves on the ground” Rainbow Dash had remarked, earning herself more than a couple glares.
At this point, the three had been lazing about for almost 2 months, and leapt at any chance to do something productive, and it really was the perfect day for shopping; nice outside, and the shops weren’t very busy.
“Okay, so, we need” Twilight started, pulling out a list as she trotted along, “diapers, bottles, pacifiers, and … hmm. We already have the Apples’ old cribs~~”
“And I’ll be making blankets~” Rarity singsonged.
“We’ve all gathered our old baby toys” Fluttershy added.
“And,” Twilight continued, unfazed by the interruptions, “and … what else? Is that it? That can’t be it.”
“Sure can! And it is!” Pinkie Pie insisted as she bounced.
“That can’t be it,” Twilight’s voice betrayed her unease, “because I don’t … I’m not ready.”
“Relaaaax Twi” Rainbow Dash said; her eyeroll was practically audible, but she smiled at her wife just the same. “We totally got this. We’re awesome.”
Applejack snorted and laughed. “Can’t possibly be as hard as fightin’ Tirek.”
“Or Discord” Fluttershy added, a giggle in her voice as well.
“Or Chrysalis”
“Nightmare Moon!”
The ponies laughed and chatted about their heroic acts of the past. Applejack, however, slowed her trot and her laughs faded to silence. “Hey, uh … girls? I feel kinda~~”
“Eeeeeeeeeee!!!!!” Pinkie squealed and danced in place.
“What? What’s happening?!” Rarity questioned, her hoof pressed to her chest in shock.
“It’s time!” Pinkie leapt into the air. “It’s time, it’s time, it’s time!!”
Twilight squeaked.
Fluttershy gingerly sat herself on the ground. “I think it’s about time for me as well”
Applejack started to wobble where she stood. “Yeah, uh. Me too.”
Rarity, Twilight, and Rainbow Dash stood frozen for a few moments.
“All three of you? At the same time?” Rarity began to hyperventilate.
In a flash of purple magic, the 6 arrived at the hospital, and were quickly taken back into a room.
Applejack, Pinkie Pie, and Fluttershy had indeed gone into labor at the same time, and went on to, hours later, give birth at the same time.
Because of this, the ponies’ foals were affectionately referred to as “the triplets” despite not actually being triplets, and “the most precious and perfect babies in the whole world” by all 6 of their mothers.