The tag implication #64407 both_pregnant -> multiple_pregnancies has been approved.

Reason: The tag "both_pregnant" implies a scene where two characters are both visibly pregnant. The tag "multiple_pregnancies" implies a scene where more than one character is visibly pregnant. I feel it is fair to make "both_pregnant" a subtag of "multiple_pregnancies".

EDIT: The tag implication both_pregnant -> multiple_pregnancies (forum #415250) has been approved by @spe.

I was going to suggest an alias as I didn't think the both_pregnant tag had much merit when multiple_pregnancies and duo exist as a tag combo. A few searches however show a distinct theme of f/f/m images with both women pregnant, which can't easily be captured without the both_pregnant tag.
Seems like this implication is the best option.

The tag implication both_pregnant -> multiple_pregnancies (forum #415250) has been approved by @spe.