<prompt> What percentage of body weight of a one year old child is TBW?90806040  <response>: Ans. is c i.e., 60 Total body water TBW as a percentage of body weight declines form as high as 90 in early fetal life to 75- 80 at birth. Thereafter it declines progressively to 60 by the end of one year. After that it remains constant. 