胎盘虽已全部剥离,由于腹肌松弛,腹压不足,或膀胱充盈阻碍胎盘娩出,影响子宫收缩而引起出血。在胎盘娩出前,不恰当地使用麦角新碱、缩宫素(催产素)等子宫收缩剂,或过早、过度地揉挤子宫,可引起子宫上段与下段交界处痉挛性收缩,形成狭窄环,使已剥离或部分剥离的胎盘嵌顿于环中,妨碍子宫收缩而出血。胎盘全部或部分粘连于子宫壁上,不能自行剥离排出,多由于子宫内膜损伤、感染或蜕膜发育不良,形成膜样胎盘、副叶胎盘或胎盘宫角附着等而不易自行剥离。全部粘连者可无出血,部分粘连者由于粘连部分影响子宫收缩,使剥离部分的血窦不能关闭,可引起大出血。由于子宫腔 Although the placenta has been fully stripped, due to abdominal muscle relaxation, abdominal pressure, or bladder filling impeded placental delivery, affecting uterine contractions and cause bleeding. Improper use of ergometrine, oxytocin (oxytocin) and other uterine contractile agents, or premature over-squeezing of the uterus before the delivery of the placenta can cause spasmodic constriction at the junction of the upper and lower uterine segments to form a stenotic ring , So that the stripped or partially peeled placenta incarcerated in the ring, hinder the contraction of the uterus bleeding. All or part of the placenta adhesion in the uterine wall, can not be stripped of their own discharge, mostly due to endometrial damage, infection or decidual dysplasia, the formation of membrane-like placenta, palate or placenta accreta placenta attached to hard to self-stripping. All adhesions without bleeding, some adhesions due to adhesions affect the contraction of the uterus, stripping part of the sinus can not be closed, can cause bleeding. Due to uterine cavity