title: Methodologic issues in assessing the active management of labor.
authors.forename: W
authors.initials: W
authors.lastname: Fraser
mesh_terms: D015982:Bias; D002585:Cesarean Section; D015986:Confounding Factors, Epidemiologic; D036861:Delivery, Obstetric / Q000379:methods*; D005260:Female; D006801:Humans; D011247:Pregnancy; D012107:Research Design / Q000592:standards