Mpreg
This tag is used when the universe where the story takes place has instances of male pregnancy, be it a rare occurrence or a norm. This tag is also used if there is a situation where a character identified as male in the universe is capable of becoming pregnant.
This tag is only used together with Pregnancy tag if the protagonist or his partner is pregnant at some point of the story. If the pregnant male is not the protagonist or his partner, do not attach Pregnancy tag together with Mpreg tag.