The placenta not only "records" and reflects the intrauterine environment, it also provides valuable information on the cause and timing of many adverse events and conditions. The placenta may be useful in several ways. It may be the cause of injury due to an inherent abnormality, it may "malfunction" because of disease processes that are not primarily placental in origin, or it may merely reflect an abnormal intrauterine environment. Not only may the etiology of the injury be ascertained from placental examination, but also a time frame during which the abnormal condition has been operating. Acute lesions may be associated with sudden catastrophic events, whereas other, more chronic lesions lead to decreased placental reserves. Markedly depleted reserves will render the infant susceptible to other, sometimes more acute, events and thus are also associated with significant injury or even death.