Abstract: Chorioamniotic membrane separation（CMS）consists of physiological and pathological form.Physiological CMS occurred before 14 gestational weeks， CMS developed after 14 gestational weeks. The damage of the fetal membrane is the initial factor of the pathological CMS. Interventional intrauterine diagnosis or treatment procedures have to pass through the unterine wall and amniotic cavity which universally causes the damage of membrane.The mild CMS had no clinical presentation， however severe CMS could increases the risk of preterm rupture of membrane，intrauterine infection，preterm delivery，amniotic band syndrome， intrauterine death. At present，more researches are needed in order to prevent the occurrence of CMS after invasive procedures. The minority of CMS is spontaneous，which is related to aneuploidy or gene mutation.The termination was mostly needed because of poor prognosis.

Key words: Chorion, Amnion, Prenatal diagnosis, Amniocentesis, Fetoscopy, Pregnancy outcome