A lack of oxygen to the brain contributes to the formation of lesions usually near the three main cerebral arteries, located near the parietal lobe and occipital lobes of the brain. The cause of perinatal brain injuries includes: 

1. cerebral ischemia
2. cerebral hemorrhage
3. ascending intrauterine infections.Some risk factors for perinatal brain injuries include: low birth weight, preterm birth, poor perinatal cardiorespiratory fitness, and artificial ventilation. Cerebral ischemia
Cerebral ischemia occurs when the brain is not receiving adequate oxygen to continue normal functions. When this occurs, the body makes restoring oxygenated blood flow to life-sustaining organs a priority. The brain alters the diameter of major blood vessels to redistribute blood to key organs such as the brain, heart, and adrenal glands. If sympathetic nervous system activation does not produce any improvement, oxygen levels will continue to fall and disruptions to metabolism, other cellular processes, and overall functioning will ensue. Another serious result of inefficient blood flow is that cells do not receive adequate amounts of glucose. An immediate effect of low intracellular glucose is reduced ATP production in the cell. This effectively inactivates the Na-K pump, leading to the uptake of calcium ions by the cell. Continued influx of calcium serves to constitutively activate downstream effectors, including lipases, proteases, and endonucleases, whose actions eventually destroy the cell skeleton. Intracellular calcium concentrations are increased further due to the opening of glutamate-regulated ion channels.
In addition, “islands” of neurons that are relatively unaffected can exist between ulegyria affected neurons. Ulegyria can develop bilaterally or unilaterally, though the former is more commonly diagnosed.Ulegyria can affect many parts of the brain including the cerebral cortex, parasagittal areas and posterior regions of the brain, such as the parietal and occipital lobes. These areas are situated either near artery rich regions or near a major cerebral artery. For instance, specifically in neonatal children, ulegyria-affected areas are found near the posterior cerebral artery or near the artery rich region between the middle and posterior regions of the brain, often referred to as watershed regions.Neurons affected by ulegyria exhibit properties that differ from normally functioning neurons. For instance, ulegyria affected neurons experience gliosis in which glial cells, specifically astrocytes, build up near and around neurons. Ulegyria affected neurons also display decreases in their white matter content, showing signs of sclerosis, which is characterized by the deterioration of myelin in neurons. However, in regions of grey matter, large dense aggregates of myelin are present. Ulegyria affected neurons also display metabolic disorders which could be linked to the disease phenylketonuria and disruptions in the urea cycle. Hypoglycemia and  hypoxia are also thought to accompany the symptoms of ulegyria-affected neurons as well. Causes
Ulegyria develops as a result of a brain injury called cerebral ischemia surrounding the time of an infants birth. Oftentimes, fetal hypoxic-ischemic brain injuries occur as a result of a pregnancy complications such as placental abruption, cord accident, or cardiovascular stress due to a difficult delivery.