PVL is caused by
decreased flow of blood & oxygen
to the white matter
of the fetal brain that surrounds the ventricles, an area susceptible to damage late in 2nd trimester, so seen more in VLBW infants.
Maternal, placental or fetal causes exist, some genetic accidents & inherited disorders, e.g., mitochondrial disorders. A Chromosomal Microarray on affected baby & genetic family history can give you some info.