Pinkie Pie and beloved husband/fellow party pony Cheese Sandwich hadn't been married long before Pinkie found out that she had a bun in the oven — or two, actually. Cherry Chimichanga had so carefully wrapped herself around her sister, Confetti Cake wasn't discovered until Pinkie had become rather rotund for just one foal, and it was discovered she was going to have twins. The rumor floating around was that Pinkie Pie was actually so jealous that her younger twin, Marble Pie had not only fallen in love, gotten married, and became pregnant first, that she wanted to jump on the bandwagon (the process of which she was quite vocal about to her friends — some believe overly so).
Twins are not very common among ponies, so Cheese and her friends kept quite a close eye on Pinkie. However, her strength and toughness as an Earth pony certainly shined during this time. She was relentless in continuing to work and bake where she could (until her poor swollen hooves just couldn't hold the mixing spoon any longer). Her emotions didn't ride the roller coaster everypony was expecting, but her cravings did go a little wild. Cheese was always immediately on the lookout for whatever his pudgy wife mentioned she was hungry for — be it watermelon or a pomegranate hayburger. Muffins were certainly a staple of her diet for quite some time.
Despite getting pregnant two weeks after her sister, Pinkie Pie was actually the one to give birth first. The pastel mare ended up falling into labor a whole two weeks early. Pinkie would later recall the terror she felt for her two new, struggling party guests would never match what she felt when facing any of Equestria's villains. However, Cheese and Mrs. Cake quite quickly fell into step and able to get Pinkie to the hospital just in time. Her two daughters were born within mere minutes. While very small, once able to get a breath, the two were quite obviously as strong as their mama.
After a few days of observation and ensuring the two were none the worse for wear, Pinkie and Cheese were able to take their new family home within a few days. The rest of her family from the rock farm traveled to Ponyville mere hours after the twins were taken home. A very nervous, incredibly round, overdue Marble Pie accompanies them. The family is relieved Pinkie is alright, and have quite a bit of fun introducing older cousins Azurite and Sandstone to the fillies. After all the excitement dies down, Pinkie realizes her own twin hasn't really interacted with her newborn nieces. She manages to coax out that Marble is terrified of motherhood. She feels better now that she's closer to the hospital, but is quite frightened of what's going to happen. Pinkie Pie thinks for a moment, rolling her sister's fear around her head. She conceded that, yes, it was going to be a pretty awful, messy, painful, and terrifying experience.
Then, she places her smallest daughter against Marble's chest. The gray mare cannot help but look over this tiny little being in wonder, her tiny limbs, her cute little nose, her little breaths, and those big blue eyes that match her mother's. Pinkie explains that the moment Marble looks over her soon-to-be son, every single second is going to be worth it. Marble holds Confetti Cake for quite some time, observing, absorbing, and thanking the little filly for helping her prepare for her own foal. As if he finally realized he was expected, Marble's son decides he's done with being out of room, and Iron Forge makes his entrance fifteen hours later. And the moment the screeching, rather heavy, squishy foal was placed on her chest where Connie rested only a day ago, feeling his heartbeat and wrapping a foreleg around him, Marble Pie steps gracefully into motherhood with a soft smile on her face. Together, she and her sisters raise a gaggle of foals that they are quite sure are going to do big things for Equestria…