Placental pathology can impair the exchange of gases across the placenta prenatally.
During labor, placental abruptio and cord accidents impair fetal perfusion and oxygenation. The effects of HIE can be compounded by traumatic lesions caused by compression of the fetal head and hyperextension of the fetal neck. Postnatally, hyaline membrane disease, persistent fetal circulation, and congenital heart disease impair oxygenation, and heart failure and shock impair cerebral perfusion. Blood loss from intraventricular hemorrhage, subcapsular hematomas of the liver and other causes may be significant. Examination of the placenta is crucial in determining the cause of perinatal HIE, but even after placental examination, the cause often remains unclear.