You, Anonymous, are a wit of the highest order :). The whole thing was brilliant, and *utterly* funny, with not a word out of place.
I'm particularly fond of the way Snape stayed Snape-ish - what usually puts me off mpreg (being Not a Fan of the concept and so prone to avoid it) is the stereotype of pregnancy that's often pasted on to the person involved. Snape was just, well, himself. Possibly more so :).