This artwork is based on a scene from Eight Inside, Enquire Within by Kassaz:

This is the version with Equestria Girls colouration and kicking.

In the fitting room with the curtain drawn, she set the shirts on a hook and started undressing. Her arms slid out of her shirt easily enough, and she quickly pulled it over her head. Her breasts had grown over the pregnancy, her diet helped, and she watched them fly upwards with her shirt before settling around the crest of her bump with a slap, only loud enough for her to barely hear it. She held the shirt in her left hand, and rested both hands on her hips as she admired herself. Perky, dark nipples and her outie navel made her midsection look like a face that had sucked on a lemon, and she giggled, making the face cross-eyed. She used her free hand to trace the dark pink linea nigra that had formed down the middle of her protrusion, from the top to just above the belly button, because that’s as far as she could reach.