This is not my model to begin with, you can find it here.
https://civitai.com/models/528370/pregnantwithclothespony

Made to work with Pony

When using the pony model to generate pregnant characters, this lora can be used to reduce the generation of belly-exposing outfits when there is no need to expose the belly.

No special tags are needed other than pregnant, and an intensity of about 1.0 is sufficient.