Reminder - Comics are "during the day" this week
I basically tripped into the hypothesis that having a lot of magic power while pregnant would pass on a lot of magic power to the child, so this wasn't a planned plot point when that hypothesis was introduced.
Nor had it been planned when the subject of Tedd's mom first came up after the mirror went haywire, as I wasn't completely certain of when Noriko (Tedd's mom) was injured, or if Edward (Tedd's dad) knew.
It was only after I considered whether Tedd's mom could have been hiding her scars while pregnant that I had that "holy carp" moment of realization, and now it's entirely possible we have an explanation for a whole bunch of things about Tedd's power.
Needless to say, I'm thrilled.