目前,血液动力学中“自我调节失控学说”在围产儿脑病变的发病机制中的作用日益为人关注。正常成人及无窒息新生儿即使在脑血流灌注压波动较大时,能通过调节脑血管阻力以维持脑血流(CBF)量恒定,窒息新生儿CBF自我调节失控,低血压及高血压可致脑缺血及毛细血管破裂。近足月胎羊实验表明SaO_2>57%,自我调节作用存在,SaO_2<50%时自我调节作用丧失,即自我调节失控的阈值为SaO_250～60%。宫内处于相对缺氧,胎儿易于出现CBF调节失控。正常分娩可致使轻度缺氧,故经阴道分娩的 At present, the role of “self-regulation out of control theory” in hemodynamics in the pathogenesis of perinatal brain lesions has drawn increasing attention. Normal adult and asphyxial newborns can maintain cerebral blood flow (CBF) constant by regulating cerebral vascular resistance even when the cerebral blood flow perfusion pressure fluctuates greatly. Asphyxial neonatal CBF regulates self-regulation, hypotension and hypertension Cause cerebral ischemia and ruptured capillaries. Nearly full-term fetal sheep experiments show that SaO_2> 57%, self-regulation exists, SaO_2 <50% loss of self-regulation, that self-regulatory threshold of loss of control SaO_250 ~ 60%. Intrauterine relative hypoxia, fetal prone to CBF regulation out of control. Normal childbirth can cause mild hypoxia, so vaginal delivery