lanugo

from WordNet (r) 3.0 (2006)

lanugo
    n 1: the fine downy hair covering a human fetus; normally shed
         during the ninth month of gestation

from The Collaborative International Dictionary of English v.0.48

Lanugo \La*nu"go\, n. [See {Lanuginose}.] (Anat.)
   The soft woolly hair which covers most parts of the mammal
   fetus, and in man is shed before or soon after birth.
   [1913 Webster]