Some placental considerations related to neurodevelopmental and other disorders.

Many newborns who appear normal at birth later manifest substantial neurologic and other disease. Pathologists are able to explain some of that sad enigma. Placental pathology frequently reveals the pathogenesis of cerebral palsy, mental retardation, and other neurodevelopmental disorders. This requires recognition of gross placental abnormalities and insightful light microscopic examination. Chorioamnionitis is now proven to be the major cause of premature onset of labor and prematurity. There is important need for investigation of pathogenetic processes associated with ascending intrauterine infection. Major complications therein include bacterially mediated fetal hypoperfusion resulting from placental and umbilical vasocontraction. Placentas of 10% of newborns have villitis of unknown etiology. The importance of villitis is incompletely known. The fetus may discharge meconium on more than one occasion, particularly so when the fetus is postmature. Clinicians may not recognize that fetal discharge has occurred if the event occurred 4 days or more prior to delivery. Intra-amniotic meconium associated with oligohydramnios probably causes placental and umbilical vasocontraction. Meconium probably thus contributes to the pathogenesis of pulmonary vasoconstriction, persistent fetal circulation, necrotizing enterocolitis, and damage of the fetal brain, liver, and kidneys. Fetal hypoxia and asphyxia may be acutely or chronically acquired. Major placental lesions associated with neonatal asphyxia include chronic ischemic change, nucleated red blood cells, intravillous hemorrhages, intimal vascular fibrin cushions, meconium staining, and intervillous fibrin.