The Collaborative International Dictionary of English v.0.48:

Abed \A*bed"\, adv. [Pref. a- in, on + bed.]
   1. In bed, or on the bed.
      [1913 Webster]

            Not to be abed after midnight.        --Shak.
      [1913 Webster]

   2. To childbed (in the phrase "brought abed," that is,
      delivered of a child). --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

abed
    adv 1: in bed