At my 20-week appt, I was up 8 lbs (with my shoes on, LOL). Doctor said I was "right on track," though I think she prefers her patients to gain on the lower spectrum (she says 20-25 lbs). I have always heard 25 to 35 was recommended.

ETA: With #1, I had gained 11 at 20 weeks (26 lbs total). It was all in my thighs and butt though. Seriously.