Multicenter, randomized, controlled trial of delayed pushing for nulliparous women in the second stage of labor with continuous epidural analgesia - Fraser, W D; Marcoux, S; Krauss, I; Douglas, J; Goulet, C; Boulvain, MThe PEOPLE (Pushing Early or Pushing Late with Epidural) Study Group. (Am J Obstet Gynecol, 2000)