Preggo Breast Plate shields?

It didn't. It's made up.

That doesn't mean that shaped armors didn't exist. They existed as a whim for wealthy aristocrats. There's quite a few instances of penis armors, for example.

https://farm5.staticflickr.com/4035/4219522544_d50cb94087_z.jpg
https://qph.fs.quoracdn.net/main-qimg-9b31219a2a73f9d6b684de49bdf79c83-c

Wealthy females, however, they were not interested in shaped armors. They'd rather buy expensive clothes with bright colors (color pigments were highly demanded and extremely expensive in middle ages). Preggo Breast armors didn't exist for a simple reason: there was no demand.