Nice bonus, I loved it😁

In your story blurb you say rarity and sweetie belle are noticing that X people are doing Y, but you don't say the 'are doing Y' part. You just put the period after listing off the characters.

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9719932
Thank you for noticing, corrected.

okay soooo why do they feel the need to get knocked up?

The story only mentions it seems to be happening, but no indication of why is given. I get it's not really suppose to be that important to the story, but I still find it a bit weird.

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Outside of Story: Because that is what the requester wanted.
Inside of Story: Personally I think the mares just are at that point where they want children.

The story felt a little repetitive. Just them being knocked up over and over. Maybe have some different variety of activities have it gradually escalate.