Looking for Reid/Maeve pregnancy fic

I recently read a really good fic (unfinished sadly) where Maeve lives and is pregnant year later but when her geneticist friend does a genetic work up she discovers that Maeve is having a set of extremely rare twins, identical but one girl and one boy. Her friend explains that Spence and Maeve won the genetic lottery when their zygote split into two, because otherwise, if it survived, the baby would have had life-long health problems.

I can't remember if it was AO3 or FF or just a oneshot on LJ.... i have searched my history but nothings coming up, no idea why.