From the first minute Grace had to walk out of the wedding, I said she's pregnant. The signs were everywhere. Anybody who knows television could call that one before halfway through the show.
Now I haven't been keeping up lately, so my only question is if Leo is supposed to be the father, or are they going to do a who's the father run for the last few episodes, ending at it being Will -- d'oh, blind-sided again (note the sarcasm).
A bigger surprise would have been if Karen said she was pregnant too!
Then again, maybe I've been watching too much Nip/Tuck. Nothing beats the twists over there.