The same artist previously made this comic: >>3646236

This comic is based on the following short story by Kassaz:
https://www.fimfiction.net/story/526921/7/short-stories-with-pregnant-ponies/cue-the-fireworks

This is the version with dialogue added by the artist.

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Two unicorns, two pegasi, and an Earth pony stood before Pinkie Pie and her mystery box. She’d told them about her plans, vaguely, and they could tell by the pair of earmuffs gripping around her belly that it was going to be something loud. She knocked off the lid, contents still unseen, and took a match from her mane; she struck it along her hoof, and tossed it in the box before hopping away with a big smile. She nearly fell over when she reached them and stopped, because all of her didn’t stop moving until she fell over onto Applejack, who gave her a displeased look.

Then there was a line of fire out of the box and into the sky, followed by an explosion, followed by more lines and explosions, all blue.

“It’s a boy!” Pinkie shouted, but nopony would be able to hear her for several hours.