People with congenital heart defects may also be prone to blood clots.Other pathological events that may result in brain ischemia include cardiorespiratory arrest, stroke, and severe irreversible brain damage.Recently, Moyamoya disease has also been identified as a potential cause for brain ischemia. Moyamoya disease is an extremely rare cerebrovascular condition that limits blood circulation to the brain, consequently leading to oxygen deprivation. Pathophysiology
During brain ischemia, the brain cannot perform aerobic metabolism due to the loss of oxygen and substrate. The brain is not able to switch to anaerobic metabolism and, because it does not have any long term energy stored, the levels of adenosine triphosphate (ATP) drop rapidly, approaching zero within 4 minutes. In the absence of biochemical energy, cells begin to lose the ability to maintain electrochemical gradients. Consequently, there is a massive influx of calcium into the cytosol, a massive release of glutamate from synaptic vesicles, lipolysis, calpain activation, and the arrest of protein synthesis. Additionally, removal of metabolic wastes is slowed. The interruption of blood flow to the brain for ten seconds results in the immediate loss of consciousness. The interruption of blood flow for twenty seconds results in the stopping of electrical activity. An area called a penumbra may result, wherein neurons do not receive enough blood to communicate, however do receive sufficient oxygenation to avoid cell death for a short period of time. Diagnosis
Classification
The broad term, "stroke" can be divided into three categories: brain ischemia, subarachnoid hemorrhage and  intracerebral hemorrhage.
Signs and symptoms
Because postterm pregnancy is a condition solely based on gestational age, there are no confirming physical signs or symptoms. While it is difficult to determine gestational age physically, infants that are born postterm may be associated with a physical condition called postmaturity. The most common symptoms for this condition are dry skin, overgrown nails, creases on the babys palms and soles of their feet, minimal fat, abundant hair on their head, and either a brown, green, or yellow discoloration of their skin. Doctors diagnose postmature birth based on the babys physical appearance and the length of the mothers pregnancy. However, some postmature babies may show no or few signs of postmaturity. Baby
Reduced placental perfusion – Once a pregnancy has surpassed the 40-week gestation period, doctors closely monitor the mother for signs of placental deterioration. Toward the end of pregnancy, calcium is deposited on the walls of blood vessels, and proteins are deposited on the surface of the placenta, which changes the placenta. This limits the blood flow through the placenta and ultimately leads to placental insufficiency, and the baby is no longer properly nourished. Induced labor is strongly encouraged if this happens. Oligohydramnios – Low volume of amniotic fluid surrounding the fetus. It is associated with complications such as cord compression, abnormal heart rate, fetal acidosis, and meconium amniotic fluid. Meconium aspiration syndrome – Respiratory compromise secondary to meconium present in infants lungs. Macrosomia – Estimated fetal weight of ≥ 4.5 kg. It can further increase the risk of prolonged labor and shoulder dystocia.